Tibia-first, gap-balanced patient-specific alignment restores bony phenotypes and joint line obliquity in a great majority of varus and straight knees and normalises valgus and severe varus deformities

PURPOSE

The present study focuses on testing the capability of a restricted tibia-first, gap-balanced patient-specific alignment technique (PSA) to restore bony morphology and phenotypes.

METHODS

Three-hundred and sixty-seven patients were treated with navigated total knee arthroplasty and tibia-first gap-balanced PSA technique. Boundaries for medial proximal tibial angle were 86°-92°, mechanical lateral distal femoral angle 86°-92°, and hip-knee-ankle angle 175°-183°. Knees were classified by coronal plane alignment of the knee (CPAK), with subsequent analyses comparing pre- and postoperative distributions. Phenotype classification within CPAK groups assessed pre- and postoperative distributions.

RESULTS

Preoperatively, the largest CPAK group was type II (30.8%), followed by type I (20.5%) and type V (17.8%). Postoperatively, type II remained the largest group (39%), followed by type V (30%). All groups with varus/valgus deformities (I, III, IV and VI) became smaller. While in straight legs (II, IV), the CPAK was restored in more than 70%-75%, in varus groups (I, IV) in 40%-50% and in valgus (III and VI) in 5%-18%. The joint line obliquity remained the same in the majority of knees (straight >75%; varus 63%-80%; valgus VI 95%), with the exception of CPAK III (40%). The phenotype analysis showed for straight legs a phenotype restoration of 85%, for varus 94% and for valgus 37%. Joint line convergence angle was reduced significantly in all groups from 1.8°-4.3° preoperatively to 0.6°-1.2° postoperatively.

CONCLUSION

PSA restores bony phenotypes and joint line obliquity in the majority of straight and varus knees, while most of the valgus and extreme varus knees are normalised.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Eight-year trajectories of malalignment progression in symptomatic knee osteoarthritis

BACKGROUND

Although various therapies have been developed to treat malalignment in osteoarthritic knees, the pattern of malalignment progression is still unclear. This study aimed to identify homogeneous subgroups with distinct trajectories of malalignment progression in subjects with symptomatic knee osteoarthritis (KOA) and to determine corresponding risk factors.

METHODS

Eight-year follow-up (from 2004 to 2012) data on 1252 participants with symptomatic KOA from the Osteoarthritis Initiative were included. Varus/valgus angle progression was characterized by group-based trajectory models. Time-varying covariates were introduced into the model to investigate how they affected trajectories. Multinomial logistic regression for trajectory group membership was applied to ascertain risk factors.

RESULTS

Five subgroups were identified. Participants in the varus worsening trajectory (n = 166) or valgus worsening trajectory (n = 118) proceeded to worsen malalignment over time. The neutral trajectory (n = 378), varus stable trajectory (n = 328), and valgus stable trajectory (n = 262) maintained close to the initial varus/valgus angle over 8 years. Higher baseline Kellgren and Lawrence grade (odds ratio [OR] = 4.35, P  < 0.001 for varus; OR = 3.85, P  < 0.001 for valgus) and "severe" baseline malalignment (OR = 13.57, P < 0.001 for varus; OR = 23.04, P < 0.001 for valgus) were risk factors for worsening trajectories. The cutoff point of the baseline varus/valgus angle to discriminate between stable or worsening trajectory was -4.5° for varus and 3.6° for valgus.

CONCLUSIONS

This study identified the malalignment progression pattern - minor malalignment (-4.5° to +3.6°) tends to remain stable, while major baseline malalignment is likely to progress. This provides a reference for therapy to prevent malalignment from deteriorating and emphasizes the necessity of determining the trigger factors for malalignment onset.

A lifespan approach to osteoarthritis prevention

Prevention is an attractive solution for the staggering and increasingly unmanageable burden of osteoarthritis. Despite this, the field of osteoarthritis prevention is relatively immature. To date, most of what is known about preventing osteoarthritis and risk factors for osteoarthritis is relative to the disease (underlying biology and pathophysiology) of osteoarthritis, with few studies considering risk factors for osteoarthritis illness, the force driving the personal, financial and societal burden. In this narrative review we will discuss what is known about osteoarthritis prevention, propose actionable prevention strategies related to obesity and joint injury which have emerged as important modifiable risk factors, identify where evidence is lacking, and give insight into what might be possible in terms of prevention by focussing on a lifespan approach to the illness of osteoarthritis, as opposed to a structural disease of the elderly. By targeting a non-specialist audience including scientists, clinicians, students, industry employees and others that are interested in osteoarthritis but who do not necessarily focus on osteoarthritis, the goal is to generate discourse and motivate inquiry which propel the field of osteoarthritis prevention into the mainstream.

Fully automated Assessment of Knee Alignment from Full-Leg X-Rays employing a "YOLOv4 And Resnet Landmark regression Algorithm" (YARLA): Data from the Osteoarthritis Initiative

BACKGROUND AND OBJECTIVE

We present a fully automated method for the quantification of knee alignment from full-leg radiographs.

METHODS

A state-of-the-art object detector, YOLOv4, was trained to locate regions of interests in full-leg radiographs for the hip joint, knee, and ankle. Residual neural networks were trained to regress landmark coordinates for each region of interest. Based on the detected landmarks the knee alignment, i.e., the hip-knee-ankle (HKA) angle was computed. The accuracy of landmark detection was evaluated by a comparison to manually placed ones for 180 radiographs. The accuracy of HKA angle computations was assessed on the basis of 2,943 radiographs by a comparison to results of two independent image reading studies (Cooke; Duryea) both publicly accessible via the Osteoarthritis Initiative. The agreement was evaluated using Spearman's Rho, weighted kappa, and regarding the correspondence of the class assignment.

RESULTS

The average deviation of landmarks manually placed by experts and automatically detected ones by our proposed "YOLOv4 And Resnet Landmark regression Algorithm" (YARLA) was less than 2.0 ± 1.5 mm for all structures. The average mismatch between HKA angle determinations of Cooke and Duryea was 0.09 ± 0.63°; YARLA resulted in a mismatch of 0.09 ± 0.73° compared to Cooke and of 0.18 ± 0.67° compared to Duryea. Cooke and Duryea agreed almost perfectly with respect to a weighted kappa value of 0.86, and showed an excellent reliability as measured by a Spearman's Rho value of 0.98. Similar values were achieved by YARLA, i.e., a weighted kappa value of 0.83 and 0.87 and a Spearman's Rho value of 0.98 and 0.98 compared to Cooke and Duryea, respectively. Cooke and Duryea agreed in 91% of all class assignments and YARLA did so in 90% against Cooke and 92% against Duryea.

CONCLUSIONS

YARLA yields HKA angles similar to those of human experts and provides a basis for an automated assessment of knee alignment in full-leg radiographs.

The accuracy of a hand-held navigation system in total knee arthroplasty

INTRODUCTION

This study aims to evaluate the effectiveness of a new hand-held navigation system. The authors of this study hypothesize that this navigation system will improve overall lower limb alignment and implant placement without causing a delay in surgery.

PATIENTS AND METHODS

Two hundred consecutive patients diagnosed with tricompartmental osteoarthritis and underwent total knee arthroplasty by a senior surgeon were included in this study. One hundred patients underwent TKA using the hand-held navigation system, while the other 100 patients underwent TKA using the conventional technique. The primary outcomes of this study were the overall alignment of the lower limb and the position of the components. This was determined radiologically using the: (1) Hip-Knee-Ankle angle (HKA) for lower limb alignment; (2) Coronal Femoral-Component angle (CFA); and (3) Coronal Tibia-Component angle (CTA) for component position. Normal alignment was taken as 180° ± 3° for the HKA and 90° ± 3° for both the CFA and CTA.

RESULTS

For the CFA, the proportion of outliers was 7 and 17% in the hand-held navigation and conventional group, respectively (p = 0.030). For the HKA and CTA, there was no difference in the proportion of outliers between the two groups. The duration of surgery was 73 ± 9 min and 87 ± 15 min in the hand-held navigation and conventional group, respectively (p < 0.001).

CONCLUSION

This hand-held navigation system is an effective intraoperative tool for reducing the proportion of outliers for femoral implant placement as well as the duration of surgery. The authors conclude that it can be considered for use to check femoral implant placement intra-operatively.

LEVEL OF EVIDENCE

III.

Effects of total knee arthroplasty on ankle alignment in patients with varus gonarthrosis: Do we sacrifice ankle to the knee?

PURPOSE

Total knee arthroplasty is one of the most commonly preferred surgical methods in the treatment of patients with varus gonarthrosis. In this study, we aimed to evaluate the radiological changes observed in the ankles after total knee arthroplasty.

METHODS

Between May 2012 and June 2013, 80 knees of 78 patients with varus deformity over 10° underwent total knee arthroplasty. For each patient, full-leg standing radiographs were obtained pre- and post-operatively. Mechanical and anatomical axes (HKA and AA), lateral distal femoral angle, medial proximal tibial angle, lateral distal tibial angle (LDTA), ankle joint line orientation angle (AJOA), tibial plafond talus angle (PTA) and talar shift were measured for each patient both pre- and post-operatively.

RESULTS

Pre-operatively, the mean HKA was 16.6° and the mean AA was 10.41°, both in favour of varus alignment. Post-operatively, the mean HKA decreased to 3.6° and the mean AA to -2.1. The mean LDTA was 87.3°. Before the operation, the mean AJOA was -7.6°, opening to the medial aspect of the ankle, and it was 0.04° after the operation and opening to the lateral aspect (p < 0.05).

CONCLUSION

Our study reveals the changes occurring in the ankle after acute correction of long-standing varus deformity of the knee using total knee arthroplasty. In cases undergoing knee arthroplasty, effect of the acute change in the alignment of the knee on the ankle should be taken into consideration and the amount of correction should be calculated carefully in order not to damage the alignment of the ankle.

LEVEL OF EVIDENCE

IV.

Sagittal placement of the femoral component in total knee arthroplasty predicts knee flexion contracture at one-year follow-up

PURPOSE

Flexion contracture has been shown to impair function and reduce satisfaction following total knee arthroplasty (TKA). The aim of this study was to identify modifiable intra-operative variables that predict post-TKA knee extension.

METHODS

Data was collected prospectively on 95 patients undergoing total knee arthroplasty, including pre-operative assessment, intra-operative computer assisted surgery (CAS) measurements and functional outcome including range of motion at one year. Patients were divided into two groups: those with mild flexion contracture (> 5°) at the one-year follow-up and those achieving full extension.

RESULTS

The sagittal orientation of the distal femoral cut differed significantly between groups at the one-year follow-up (p = 0.014). Sagittal alignment of greater than 3.5° from the mechanical axis was shown to increase the relative risk of a mild flexion contracture at one-year follow-up by 2.9 times, independent of other variables.

CONCLUSION

Increasing the sagittal alignment of the distal femoral cut more than 3.5° from the mechanical axis is an independent risk factor for clinically detectable flexion contracture one year from index procedure.

Accuracy of the acetabular index using the percutaneous assisted total hip technique

In minimally invasive total hip arthroplasty (THA), proper acetabular component positioning can be difficult to achieve without navigational or intraoperative radiographic methods. Acetabular components placed in excessive abduction can lead to early failure and dislocation. This article describes a series of 74 consecutive primary THAs (71 patients, 3 bilateral) performed using a percutaneous assisted THA technique that does not require navigation, yet allows adequate visualization for accurate acetabular cup placement. No patients were excluded (because of body mass index or abnormal anatomy) from the study. Mean abduction angle for all hips was 45°. The goal was acetabular abduction angle between 35° and 55°. This goal was achieved in 72 of the 74 hips (97.3%). Proper acetabular abduction angle can be achieved in the majority of cases using this new soft-tissue sparing approach for THA.

[Imaging of knee prostheses]

The authors present a pictorial essay illustrating the different types of knee prostheses, their normal appearances, as well as the imaging features (radiographs, CT, US) of the main complications that may occur.

Fracture of fully coated echelon femoral stems in revision total hip arthroplasty

Three cases of fractured uncemented, fully porous Echelon femoral stems (Smith & Nephew, Memphis, Tenn) are examined. Fracture of these components, an uncommon complication of revision hip surgery, is thought to result from cantilever bending after distal bony ingrowth. The stems in these cases fractured at 11, 22, and 28 months after revision surgery. Risk factors include increased body weight, excessive activity, an undersized stem, varus alignment, inadequate proximal femoral bone stock, and metallurgic defects. Extraction can be difficult and is often accomplished with the use of multiple trephines or via tamping through a distal cortical window.

Static knee alignment is associated with the risk of unicompartmental knee cartilage defects

Although knee malalignment is a risk factor for the progression of unicompartmental knee osteoarthritis (OA), it is unclear how this relationship is mediated. Cartilage defects are known to predate cartilage loss and the onset of knee OA, and it may be that knee malalignment increases the risk of unicompartmental knee cartilage defects. Knee radiographs and MRI were performed on a total of 202 subjects, 36.6% of whom had radiographic knee OA, to determine the relationship between static knee alignment and knee cartilage defects. Analyses were performed for the entire cohort, as well as for healthy and OA subgroups. For every 1 degrees increase in a valgus direction, there was an associated reduced risk of the presence of cartilage defects in the medial compartment of subjects with knee OA (p = 0.02), healthy subjects (p = 0.002), and the combined (p < 0.001) group. Moreover, for every 1 degrees increase in a valgus direction, there was an associated increased risk of the presence of lateral cartilage defects in the OA group (p = 0.006), although the relationship between change toward genu valgum and lateral compartment cartilage defects did not persist for the healthy group (p = 0.16). This cross-sectional study has demonstrated that knee alignment is associated with the risk for compartment specific knee cartilage defects in both healthy and arthritic people. Given that the natural history of cartilage volume reduction appears to be predated by the presence of cartilage defects, whether knee alignment affects the longitudinal progression from cartilage defects to cartilage loss requires further examination.

Sex differences in clinical measures of lower extremity alignment

STUDY DESIGN

Descriptive, cohort design.

OBJECTIVES

To comprehensively examine sex differences in clinical measures of static lower extremity alignment (LEA).

BACKGROUND

Sex differences in LEA have been included among a myriad of risk factors as a potential cause for the increased prevalence of knee injury in females. While clinical observations suggest that sex differences in LEA exist, little empirical data are available to support these sex differences or the normal values that should be expected in a healthy population.

METHODS AND MEASURES

The right and left static LEA of 100 healthy college-age participants (50 males [mean +/- SD age, 23.3 +/- 3.6 years; height, 177.8 +/- 8.0 cm, body mass, 80.4 +/- 11.6 kg] and 50 females [mean +/- SD age, 21.8 +/- 2.5 years; height, 164.3 +/- 6.9 cm; body mass, 67.4 +/- 15.2 kg]) was measured. Each alignment characteristic was analyzed via separate repeated-measures analyses of variance, with 1 between-subject factor (sex) and 1 within-subject factor (side).

RESULTS

There were no significant sex-by-side interactions and no differences between sides. Females had greater mean anterior pelvic tilt, hip anteversion, quadriceps angles, tibiofemoral angles, and genu recurvatum than males (P < .0001). No sex differences were observed in tibial torsion (P = .131), navicular drop (P = .130), and rearfoot angle (P = .590).

CONCLUSION

Sex differences in LEA indicate that females, on average, have greater anterior pelvic tilt, thigh internal rotation, knee valgus, and genu recurvatum. These sex differences were not accompanied by differences in the lower leg, ankle, and foot. Understanding these collective sex differences in LEA may help us to better examine the influence of LEA on dynamic lower extremity function and clarify their role as a potential injury risk factor.

Management of lower extremity malalignment during running with neuromuscular retraining of the proximal stabilizers

This case report presents a high-level female runner with a history of more than 25 years of recurrent lower extremity (LE) injuries and LE malalignment problems during running. Due to her LE malalignment, she has been unable to run for the past 3 years. A definitive diagnosis was not found for her inability to run so by exclusion we diagnosed dysfunction of the hip, spine, and pelvic stabilizers that resulted in her in LE malalignment. To treat this muscle weakness, we designed a Pilates-evolved functional movement intervention to improve the control and strength of the proximal stabilizers and regain normal LE alignment. The Pilates-evolved treatment approach involved a series of functional and progressive resistance exercises designed to dynamically stabilize the spine, pelvis, and hip through all planes of motion. After 1 year of Pilates-evolved training, the athlete's disabling movement pattern resolved and she has returned to a regular running program. The purpose of this case report is to describe a Pilates-evolved functional movement intervention that resolved this runner's LE malalignment and returned her to running when other traditional treatment approaches were not effective in doing so.

Axial radiography of the distal femur to assess rotational alignment in total knee arthroplasty

A method for taking an axial radiograph of the distal femur was developed to see the epicondyles and posterior condyles of the femur. It was hypothesized that these radiographs would be acceptable for evaluating rotational alignment in total knee arthroplasty with comparable reproducibility and good correlation to the results obtained with computed tomography images. Radiographs were obtained of 50 knees in 32 patients having total knee arthroplasty. The radiographs were taken while the patients were with the knee in 90 degrees flexion. The angle between the clinical epicondylar axis and the posterior condylar axis (twist angle) was measured and compared with the results obtained by conventional computed tomography. The interobserver variation in the axial radiography was less than or comparable to the computed tomography method. The mean discrepancy between the two methods (+/- standard deviation) was 0.5 degrees +/- 0.4 degrees (range, 0-1.9 degrees ), and a strong correlation was observed. This plain radiography is acceptable for evaluation of femoral component rotation with comparable reproducibility and correlation to the results with computed tomography. It has several advantages regarding cost, radiation dose, and lack of scatter when used for postoperative assessment.

Hip strength in females with and without patellofemoral pain

STUDY DESIGN

Cross-sectional.

OBJECTIVES

To determine if females with anterior knee pain are more likely to demonstrate hip abduction or external rotation weakness than a similar, asymptomatic, age-matched control group.

BACKGROUND

Diminished hip strength has been implicated as being contributory to lower-extremity malalignment and patellofemoral pain. The identification of reliable and consistent patterns of weakness in this population may assist health care professionals establish a more effective treatment plan.

METHODS AND MEASURES

Hip abduction and external rotation isometric strength measurements were recorded for the injured side of 15 female subjects with patellofemoral joint pain (mean +/- SD age, 15.7 +/- 2.7 years; age range, 12-21 years). These were compared with strength measurements from the corresponding hip of 15 age-matched female control subjects (mean +/- SD age, 15.7 +/- 2.7 years; age range, 12-21 years). All strength measurements were made using hand-held dynamometers.

RESULTS

Subjects with patellofemoral pain demonstrated 26% less hip abduction strength (P<.001) and 36% less hip external rotation strength (P<.001) than similar age-matched controls.

CONCLUSIONS

The results indicate that young women with patellofemoral pain are more likely to demonstrate weakness in hip abduction as well as external rotation than age-matched women who are not symptomatic.

[Rotational malalignment of the components may cause chronic pain or early failure in total knee arthroplasty]

Rotational alignment of the tibial and femoral component plays an important role in modern total knee replacement surgery. After correct frontal alignment and proper soft tissue balancing, the rotational placement of the components represents the "third dimension" in knee endoprosthetic surgery. Improved surgical techniques with modified instruments and better rotational component positioning will lead to better functional outcomes. Patients with painful total knee arthroplasties (TKA) or early failure without evident classic implantation failures or signs of infection should be evaluated for malrotation of the components. In a prospective study in 26 patients with painful TKA and malrotation of the tibia and/or femur component, revision surgery with exchange of the components was performed. Twenty-five cases showed clinically relevant internal malrotation of the tibial component (ø 8.4 degrees ) and/or femoral component (ø 5.6 degrees ). Only one patient had 10 degrees of external malrotation of the femoral component. Combined malrotations of the tibia and femur were found in ten knees (38%). After revision surgery and correction of malrotations, 20 patients (78%) were scored with excellent and good results. Patients with painful TKA resistant to conservative therapy and evident malrotations of the component should be considered for revision surgery with change of the malrotated components.

The effect of component malalignment on the clinical and radiological outcome of the Kinemax total knee replacement

Component angles of 198 Kinemax total knee replacements were measured from standard short leg radiographs. An ideal tibio-femoral angle of between 4 and 10 degrees of valgus was achieved in 64.6% of patients. After an average follow-up of 6.5 years (range 4.5 to 9.5), there was no significant difference between knees in acceptable and suboptimal alignment in terms of pre- and post-operative knee and function scores and prevalence of radiolucent lines. Varus placement of the tibial component was significantly more common by trainee surgeons (P<0.001).

Linear and volumetric wear of tibial inserts in posterior cruciate-retaining knee arthroplasties

Linear and volumetric wear was measured in 33 tibial polyethylene inserts from three different cruciate-retaining knee systems retrieved at the time of revision surgery. Wear patterns also were evaluated and classified. Eccentric and asymmetric wear patterns were seen in 78% of inserts with flat articulating geometry versus 12% in inserts with curved anteroposterior geometry. The mean linear wear rate was .35 mm/year (range, .05-1.68 mm/year) and the mean volumetric wear rate was 794 mm3/year (range, 24-4088 mm3/year). Linear and volumetric wear rates showed a negative correlation with the length of implantation. Linear wear rates also showed a negative correlation with patient weight.

Effect of femoral component rotation and patellar design on patellar forces

A force transducer attached to the patella was used to measure patellar contact forces after total knee arthroplasty for neutral femoral component position and for 10 degrees internal and external femoral component rotations. Knees were cycled continuously under load from 10 degrees to 110 degrees flexion. Two designs of knee replacement with differing degrees of intrinsic tibiofemoral constraint were studied. Additionally, contact forces for a dome shaped patella and a modified dome shaped patella (a patellar component with a central projection surrounded by a peripheral flat region) were compared. When using the design with relatively high intrinsic tibiofemoral constraint, there were no significant changes in patellar contact forces after axial rotation of the femoral component. When using the design with relatively low intrinsic tibiofemoral constraint and averaging over the range of flexion angles tested, the mediolateral component of the patellar contact force increased approximately 17% after 10 degrees internal rotation compared with neutral rotation, and the normal component of the patellar contact force decreased approximately 8% after a 10 degrees external rotation compared with 10 degrees internal rotation of the femoral component. The inferosuperior component of the patellar shear force, when using the modified dome shaped patellar component, was significantly lower than for the dome shaped patella.

Flat-on-flat, nonconstrained, compression molded polyethylene total knee replacement

Flat-on-flat, posterior cruciate ligament-sparing total knee prostheses recently have shown problems of wear, loosening, and multiple design changes. Two thousand one Anatomical Graduated Components total knee arthroplasties with compression molded, nonmodular polyethylene tibial components were done between 1983 and 1991 at 3 institutions. All knees were evaluated clinically and radiographically every 2 to 3 years; 71 knees were seen in followup > 10 years. There were 8 failures secondary to revision (5 tibial failures; 2 secondary to metalosis from patellar polyethylene dissociation; and 3 femoral failures) resulting in a 98% survival rate at 10 years. The tibial design was flat-on-flat with a compression molded polyethylene that the authors believe is the primary reason for its success.

Influence of malalignment of feet on the plantar pressure pattern in running

When overuse injuries of the lower limbs are diagnosed in athletes, the architecture and function of the foot should be examined. Foot structure was evaluated in 10 male and 14 female athletes. Based on this examination, the subjects were classified into three groups: pes planus, pes cavus, and pes rectus. While running, the plantar pressure pattern of these athletes was assessed with pressure-measuring insoles. Using these measurements, peak pressures and impulses were calculated for different foot anatomical locations. The plantar heel load was distributed significantly (P < 0.05) more toward the anterior part of the calcaneus in the pes planus group compared with the normal group. The relative load under the midfoot region was significantly (P < 0.05) lower in the pes cavus group compared with the other foot types. The relative load of the forefoot was significantly (P < 0.05) higher in the pes cavus group and lower in the pes planus group. Both feet of an athlete showed a similar plantar pressure pattern. Three successive steps were comparable in terms of impulses, but the peak pressures varied significantly from step to step. The local impulse and peak pressure values obtained in barefoot running differed significantly from the values obtained in running with sport shoes.