Strong correlation between the morphology of the proximal femur and the geometry of the distal femoral trochlea

Hip and pelvic geometry as predictors of knee osteoarthritis severity

Malalignment is one of the most critical risk factors for knee osteoarthritis (KOA). Biomechanical factors such as knee varus or valgus, hip-knee-ankle angle, and femoral anteversion affect KOA severity. In this study, we aimed to investigate KOA severity predictive factors based on hip and pelvic radiographic geometry. In this cross-sectional study, 125 patients with idiopathic KOA were enrolled. Two investigators evaluated the knee and pelvic radiographs of 125 patients, and 16 radiological parameters were measured separately. KOA severity was categorized based on the medial tibiofemoral joint space widths (JSW). Based on JSW measurements, 16% (n = 40), 8.8% (n = 22), 16.4% (n = 41), and 56.8% (n = 147) were defined as grades 0, 1, 2, 3, respectively. There were significant differences between the JSW groups with respect to hip axis length, femoral neck-axis length, acetabular width, neck shaft angle (NSA), outer pelvic diameter, midpelvis-caput distance, acetabular-acetabular distance, and femoral head to femoral head length (P < .05). Two different functions were obtained using machine learning classification and logistic regression, and the accuracy of predicting was 74.4% by using 1 and 89.6% by using both functions. Our findings revealed that some hip and pelvic geometry measurements could affect the severity of KOA. Furthermore, logistic functions using predictive factors of hip and pelvic geometry can predict the severity of KOA with acceptable accuracy, and it could be used in clinical decisions.

Stem Design in Total Hip Arthroplasty Influences Ipsilateral Knee Valgus: A Retrospective Comparative Analysis of 2953 Cases

BACKGROUND

Total hip arthroplasty (THA) affects the biomechanics of the hip and the patient gait. The stem design influences femoral lever ratios and tissue trauma. Biomechanical changes such as these have the potential to induce knee arthritis. A varus or valgus configuration of knee arthritis is formed by asymmetric loadings. The aim of this study was to evaluate the impact of stem design in THA on knee valgus by comparing a standard implant with an implant with a short stem.

METHODS

A total of 2953 patients who underwent primary total knee arthroplasty for end-stage osteoarthritis between 2015 and 2021 were included in this retrospective data analysis. Patients were divided into three groups, depending on hip status (straight stem, short stem, and native joint). Leg alignment was distinguished as varus or valgus, and the degree of axial deviation was measured. Descriptive and explorative statistical analyses were performed, with a p value < 0.05 set as significant.

RESULTS

Ipsilateral knee valgus occurred significantly more often in patients with straight stems (57.2%) than in those with short stems (29%) and native joints (25.8%) (p < 0.001). Additionally, mean valgus deviation was significantly increased in patients with straight stems (8.9°) compared to those with short stems (6.4°) or native hip joints (6.7°). Both findings were accentuated in women.

CONCLUSIONS

Previous ipsilateral straight-stem THA is associated with knee valgus deformity, especially in women. Short-stem THA seems to be better suited to restoring physiological biomechanics and preventing the development of valgus osteoarthritis of the ipsilateral knee.

Local torsion of distal femur is a risk factor for patellar dislocation

PURPOSE

It has been widely reported that femoral anteversion is a risk factor for patellar dislocation. This study aims to evaluate whether internal torsion of the distal femur is noticeable in patients without increased femoral anteversion and to assess whether it is a risk factor for patellar dislocation.

METHODS

A retrospective analysis was conducted on 35 patients (24 females, 11 males) with recurrent patellar dislocation but without increased femoral anteversion treated in our hospital from January 2019 to August 2020. All patients underwent knee X-rays, digital radiography of lower-limbs, and CT scans of hip, knee, and ankle joints to measure femoral anteversion angle, distal femoral torsion angle, TT-TG and Caton-Deschamps index. Thirty-five control cases were matched on age and sex to compare the difference of anatomic parameters between the two groups, and the logistic analysis was used to analyze risk factors for patellar dislocation. Perman correlation coefficient was used to evaluate the correlation among femoral anteversion, distal femoral torsion and TT-TG.

RESULTS

Greater distal femoral torsion was still observed in patients with patellar dislocation but without increased femoral anteversion. The torsion angle of distal femur, TT-TG distance and incidence of Patella Alta in patients with patellar dislocation were greater than those in control group, and the inter-group differences were statistically significant (P < 0.05). The torsion angle of distal femur (OR = 2.848, P < 0.001), TT-TG distance (OR = 1.163, P = 0.021) and Patella Alta (OR = 3.545, P = 0.034) were risk factors for patellar dislocation. However, no significant correlation was found among femoral anteversion, distal femoral torsion and TT-TG in patients with patellar dislocation.

CONCLUSION

On the condition that femoral anteversion did not increase, increased distal femoral torsion was commonly observed in patients with patellar dislocation, which represents an independent risk factor for patellar dislocation.

Patients with varus knee osteoarthritis undergoing high tibial osteotomy exhibit more femoral varus but similar tibial morphology compared to non-arthritic varus knees

PURPOSE

The aim of this study was to compare alignment parameters between patients undergoing high tibial osteotomy (HTO) for knee osteoarthritis (OA) and non-arthritic controls.

METHODS

Pre-operative computed tomography images from 194 patients undergoing HTO for medial knee OA and 118 non-arthritic controls were utilized. All patients had varus knee alignment (mean age: 57 ± 11 years; 45% female). The hip-knee-ankle (HKA) angle, mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA) and non-weight-bearing joint line convergence angle (nwJLCA) were compared between "control group" and "HTO group". Femoral and tibial phenotypes were also assessed and compared between groups. Variables found on univariate analysis to be different between the groups were entered into a binary logistic regression model.

RESULTS

The mean age was lower (Δ = 4 ± 6 years, p = 0.024), body mass index (BMI) was higher (Δ = 1.1 ± 2.8 kg/m², p = 0.032) and there were more females (Δ = 14%, p = 0.020) in the HTO group. The HTO group had more overall varus (7° ± 4.7° vs 4.8° ± 1.3°, p < 0.001). There was a significant difference in the mean mLDFA between the two groups with the HTO group having more femoral varus (88.7 ± 3.2° vs 87.3 ± 1.8°, p < 0.001). MPTA was similar between the groups (p = 0.881). Age was found to be a strong determinant for femoral varus (p = 0.03).

CONCLUSION

Patients undergoing HTO for medial knee OA have more femoral varus compared to non-arthritic controls while tibial morphology was similar. This will be an important consideration in pre-operating planning for realignment osteotomy in patients presenting with medial knee OA and warrants further investigation.

LEVEL OF EVIDENCE

III, retrospective comparative study.

Bony asymmetry in patellofemoral morphology and risk factors of instability are mostly clinically negligible

PURPOSE

Previous investigations suggested that femoral side-to-side differences were located in the upper femur anatomy. However, little is known about the asymmetry between distal femur and patella. The degree of bony asymmetry in the patellofemoral joint was evaluated using pairs of CT-scans with emphasis on morphometric measurements and risk factors relevant to patellofemoral disorders.

METHODS

Patellofemoral morphometric parameters and anatomical risk factors were analyzed from 345 pairs of CT scans to evaluate side-to-side differences for each patient. All measurements were automatized using previously published algorithm-calculated bone landmarks. We analyzed asymmetry based on absolute differences (AD) and percentage asymmetry (AS%). Significant asymmetry was defined as AS% > 10%.

RESULTS

Patellar height was found to be highly symmetric (mean AD 0.1 for both Insall-Salvatti and Caton-Deschamps methods, AS% 8% and 9%, respectively). Patellar and femoral morphometric parameters were found highly symmetric, except for the trochlear groove depth. Substantial asymmetry was reported in two patellofemoral risk factors: the lateral trochlear inclination (mean AD 2°, AS% 16%) and the tibial tuberosity-trochlear groove distance (1 mm, 116%). Patellar and femoral morphometric asymmetries were independent of demographics, including age, gender, height, weight and ethnicity.

CONCLUSION

Patellar height was found to be highly symmetric and is, therefore, a reasonable index for contralateral templating. While very few patellofemoral morphometric parameters and anatomical risk factors were asymmetric, the mean differences were clinically negligible and independent of demographics.

LEVEL OF EVIDENCE

III.

An association between femoral trochlear morphology and non-contact anterior cruciate ligament total rupture: a retrospective MRI study

INTRODUCTION

The present study aims to investigate the association of the femoral trochlear morphology with the risk of ACL injury and whether this can be considered an additional risk factor in this clinical table.

MATERIALS AND METHODS

This is a retrospective case-control study with 93 patients, 41 patients with ACL total rupture (ACL-TR), and 52 patients without ACL injury who underwent knee magnetic resonance imaging (MRI) between January 2013 and January 2016. The femoral trochlear morphology was evaluated at the proximal and distal levels from the axial knee MRI. The morphological features of the trochlea using sulcus angle, sulcus depth, condylar heights, trochlear sulcus height, percentage of condyles and trochlear sulcus height to transepicondylar width, and lateral and medial trochlear inclination were evaluated. The notch width index was measured on the coronal MR images for notch stenos.

RESULTS

ACL-TR group had a significantly higher sulcus angle (p = 0.00-0.001) and lower sulcus depth (p = 0.00-0.002) than the control group at both levels. Femoral trochlea had morphometric differences between genders. NWI was lower in the ACL-TR group than the control group (control 0.273; ACL-TR 0.247), and there was a statistically significant difference (p = 0.00).

CONCLUSION

This study was shown that the difference in morphology between the trochlear sulcus of patients with normal and ACL injuries should be taken into account in order to increase awareness of ACL injuries. We observed that mild trochlear dysplasia may cause intercondylar notch stenosis rather than changing the localization of the patella. Studies are needed regarding the effect of trochlear dysplasia on ACL.

Sexual and ethnic polymorphism result in considerable mismatch between native trochlear geometry and off-the-shelf TKA prostheses

PURPOSE

To determine if trochlear morphology in healthy knees depends on sex and ethnicity, and to compare it to off-the-shelf TKA prostheses.

METHODS

Three retrospective series of CT angiograms from France (female, 124; male, 135), China (female, 122; male, 137) and South Africa (female, 21; male, 62) were used to digitize osseous landmarks at the level of the femoral epicondyles. Sulcus angle, trochlear rotation, lateral trochlear inclination, trochlear asymmetry ratio, and trochlear depth index were quantified for each knee and for 10 total knee arthroplasty (TKA) models. Univariable regression analyses were performed to determine associations of the five trochlear parameters with sex and ethnicity. Interquartile ranges (IQR) of native trochlear parameters were compared to the trochlear parameters of 10 off-the-shelf TKA prostheses.

RESULTS

Compared to French knees, Chinese knees had greater sulcus angle (β = 6.3°, p < 0.001), trochlear rotation (β = 0.8°, p = 0.004) and trochlear depth index (β = 1.60, p < 0.001). Conversely, South African knees had greater trochlear rotation (β = 1.9°, p < 0.001) and lateral trochlear inclination (β = 3.7°, p < 0.001). Female knees had smaller trochlear asymmetry ratios (β =  - 0.03, p = 0.05) but greater trochlear rotation angles (β = 0.7, p = 0.005). Considerable mismatches in trochlear morphology were revealed between native knees and off-the-shelf TKA prostheses.

CONCLUSIONS

The findings suggest that thresholds used in the diagnosis of patellofemoral instability should be adapted to patient sex and ethnicity, and that standard off-the-shelf TKA may not restore native trochlear parameters in all patients.

LEVEL OF EVIDENCE

III, retrospective comparative.

A landmark-based 3D analysis reveals a narrower tibial plateau and patella in trochlear dysplastic knees

PURPOSE

The trochlear dysplastic femur has a specific morphotype previously characterised by not only dysplastic features of the trochlea but also by specific features of the notch and posterior femur. In this study the morphology of the tibia and patella was investigated to gain further insight in the complete geometrical complexity of the trochlear dysplastic knee.

METHODS

Arthro-CT scan-based 3D models of 20 trochlear dysplastic and 20 normal knees were uniformly scaled and landmarks and landmark-based reference planes were created to quantify a series of morphometric characteristics of the tibia and patella.

RESULTS

In the mediolateral direction, the 3D-analysis revealed a 3% smaller medial tibial plateau (30.4 ± 1.6 mm vs 31.5 ± 1.6 mm), a 3% smaller overall width of the tibial plateau (73.6 ± 2.0 mm vs 75.7 ± 2.0 mm), a 16% smaller medial facet (17.3 ± 2.2 mm vs 20.1 ± 1.3 mm) and a 4% smaller overall width of the patella (41.7 ± 2.5 mm vs 43.4 ± 2.3 mm) in trochlear dysplastic knees. In the anteroposterior direction, the lateral tibial plateau of trochlear dysplastic knees was 5% larger (37.2 ± 2.3 mm vs 35.5 ± 3.1 mm). A correlation test between the width of the femur and the width of the tibia revealed that trochlear dysplastic knees show less correspondence between the femur and tibia compared to normal knees.

CONCLUSION

Significant differences in the morphology of the tibial plateau and patella were detected between trochlear dysplastic and normal knees. Both in the trochlear dysplastic tibial plateau and patella a narrower medial compartment leads to a significant smaller overall mediolateral width. These findings are important for the understanding of knee biomechanics and the design of total knee arthroplasty components.

LEVEL OF EVIDENCE

III.

Hybrid high tibial osteotomy is superior to medial opening high tibial osteotomy for the treatment of varus knee with patellofemoral osteoarthritis

PURPOSE

To evaluate patellofemoral congruity after opening wedge high tibial osteotomy (OWHTO) and hybrid HTO.

METHODS

Twenty-four knees with hybrid HTO and 24 with OWHTO were evaluated in this study. The Caton-Deschamps and modified Miura-Kawamura indices were used to evaluate pre- and post-operative patellar heights for both types of surgery. Tibial tuberosity-trochlear groove (TT-TG) distance, patellar tilt, and medial and lateral joint space at the patellofemoral joint were compared. Anterior knee pain was assessed using the Kujala anterior knee pain scale.

RESULTS

There was no significant difference between the correction angles of the hybrid HTO and OWHTO. Pre- and post-operative values for the Caton-Deschamps and modified Miura-Kawamura indices in patients who underwent hybrid HTO changed from 0.90 to 0.94 and from 0.95 to 1.03, respectively, with no significant differences noted. Following OWHTO, these values decreased significantly from 0.91 to 0.73 and from 1.06 to 0.84, respectively (p < 0.01). The post-operative patellar height after OWHTO was significantly lower than that after hybrid HTO (p < 0.01). After hybrid HTO, the TT-TG distance decreased significantly from 11.4 to 7.4 (p < 0.01), but it did not change significantly after OWHTO. Although pre- and post-operative patellar tilt were not altered significantly in either group, the medial joint space of the patellofemoral joint was significantly increased post-operatively following hybrid HTO (p = 0.035). The pre-operative Kujala scores were significantly lower in the hybrid HTO group, but post-operative scores improved in both groups.

CONCLUSIONS

Hybrid HTO provides a better post-operative patellofemoral joint than does OWHTO with regard to patellar position and reduction of the TT-TG distance, as well as improved clinical outcomes. Hybrid HTO, rather than OWHTO, is the preferred technique for the treatment of varus knees combined with patellofemoral osteoarthritis.

LEVEL OF EVIDENCE

Retrospective comparative study, Level III.

Distal Femoral Rotation is not Associated With Preoperative Proximal Tibial Varus Angle in Patients With Isolated Medial Compartment Osteoarthritis

BACKGROUND

Prior studies have found that greater proximal tibial varus was associated with increased external femoral rotation at time of total knee arthroplasty. These works suggest that measuring the tibial plateau-tibial shaft (TPTS) angle on preoperative weight-bearing long leg radiographs could predict significant variations in the posterior condylar angle.

METHODS

A minimum of 68 patients were needed to reach 80% power. Patients were included if they had primary medial compartment osteoarthritis and excluded if they had a valgus mechanical axis. The clinical posterior condylar angle (cPCA) was defined as the angle between the anatomic transepicondylar axis and posterior condylar line. Correlation analyses were performed to test for any relationship between the TPTS and cPCA. Two patient groups were created based on TPTS angle: TPTS ≤4° (mild varus) and TPTS >4° (moderate varus). Mechanical axis and rotational measurements were compared between the groups using independent t-tests.

RESULTS

The mean mechanical axis and TPTS angle were 6.9° and 4.8° of varus, respectively. The mean cPCA was 5.0° (standard deviation [SD], 1.4°; range, 2.4°-7.9°). No correlation was found between the TPTS angle and cPCA (P = .15). The mean cPCA in the mild varus group (n = 28 patients) was 5.2° (SD, 1.5°; range, 2.7°-7.9°), and the mean cPCA in the moderate varus group (n = 45 patients) was 4.4° (SD, 1.7°; range, 0.6°-7.5°). These groups were not statistically significantly different from each other (P = .62).

CONCLUSION

The present study does not support the conclusions of previous works and suggests that the amount of distal femoral rotation cannot be predicted by tibial varus alignment measured on preoperative long leg radiographs. Consequently, we believe that proximal tibial varus should not be used to preoperatively predict external rotation of the femoral component in patients with isolated medial compartment osteoarthritis.

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.

The Hip Morphology Changes with Ageing in Asian Population

Objectives

This study aims to determine the changing in hip anatomy parameters with age and reveals the reason for the extorsion of lower extremity in the aged.

Design

Retrospective study.

Participants

One hundred and forty patients who had received imaging check of the femur and acetabulum between October 2013 and October 2016 were included in this study.

Main Outcome Measures

The femoral neck torsion angle (FNTA), neck-shaft angle (NSA), and acetabular anteversion angle (AVA) were measured by an experienced orthopedic surgeon. All the patients' demographic and physical characteristics including age, sex, body laterality, height, and weight were recorded. The Student t-test, two-way ANOVA, Pearson correlation, and multiple linear regression were used for the statistical analysis.

Results

The mean age for male and female was 45.01±15.38 and 49.30±17.63 years, respectively. Outcomes revealed that the NSA on the right side of the body, 133.46±4.46° in male and 134.36±4.71° in female, was statistically higher than the left side. Female FNTA had significantly higher values than male (P<0.01). Two-way ANOVA reveals that FNTA and AVA were correlated with age (P<0.05) but not weight, height, or BMI. NSA was correlated with age, weight, and BMI (P<0.05) but not height. Multiple linear regression analysis showed that only age made an independent contribution to NSA.

Conclusions

The NSA and FNTA of Asian population may have an obvious decrease whereas AVA increases with ageing, which reveals the reason for the extorsion of lower extremity with elderly. During hip-related surgery in elderly patients, more attention should be paid to these lower extremity anatomic changes.

Proximal and distal alignment of normal canine femurs: A morphometric analysis

Many researchers are interested in femoral conformation because most orthopaedic problems of the long bones occur in the femur and its joints. The neck-shaft (NSA) and the anteversion (AVA) angles are good predictors for understanding the orientation of the proximal end of the femur. The varus (aLDFA) and procurvatum (CDFA) angles have also been used to understand the orientation of the distal end of the femur. The purposes of this study were to investigate the relationship between the proximal and distal angles of the femur and to compare the distal femoral angles in male and female dogs in order to investigate the sexual dimorphism. The measurements of normal CDFAs, which have not been previously reported, may also provide a database of canine distal femoral morphology. A total of 75 cleaned healthy femora from different breeds or mixed breed of dogs were used. The three-dimensional images were reconstructed from computed tomographic images. The AVA, NSA, aLDFA and CDFA were measured on the 3D images. The correlation coefficients were calculated among the measured angles. The distal femoral angles were also compared between male and female femora. The 95% confidence intervals of the AVA and the NSA were calculated to be 24.22°-29.50° and 144.97°-147.50°, respectively. The 95% confidence intervals of the aLDFA and the CDFA for all studied dogs were 92.62°-94.08° and 89.09°-91.94°, respectively. The NSA showed no correlation with either the aLDFA or CDFA. There was a weak inverse correlation between the AVA and CDFA and a weak positive correlation between the AVA and aLDFA. The differences in the aLDFA and CDFA measurements between male and female dog were not significant. In conclusion, femoral version, regardless of the plane, might have little influence on distal femoral morphology in normal dogs. Besides this, there is no evidence of a sexual dimorphism in the varus and procurvatum angles of the dog distal femur. The data from this study may be used in both orthopaedic studies and for clinical applications related to the distal femur of dogs.

Evaluation of a modified knee rotation angle in MRI scans with and without trochlear dysplasia: a parameter independent of knee size and trochlear morphology

PURPOSE

Regarding TT-TG in knee realignment surgery, two aspects have to be considered: first, there might be flaws in using absolute values for TT-TG, ignoring the knee size of the individual. Second, in high-grade trochlear dysplasia with a dome-shaped trochlea, measurement of TT-TG has proven to lack precision and reliability. The purpose of this examination was to establish a knee rotation angle, independent of the size of the individual knee and unaffected by a dysplastic trochlea.

METHODS

A total of 114 consecutive MRI scans of knee joints were analysed by two observers, retrospectively. Of these, 59 were obtained from patients with trochlear dysplasia, and another 55 were obtained from patients presenting with a different pathology of the knee joint. Trochlear dysplasia was classified into low grade and high grade. TT-TG was measured according to the method described by Schoettle et al. In addition, a modified knee rotation angle was assessed. Interobserver reliability of the knee rotation angle and its correlation with TT-TG was calculated.

RESULTS

The knee rotation angle showed good correlation with TT-TG in the readings of observer 1 and observer 2. Interobserver correlation of the parameter showed excellent values for the scans with normal trochlea, low-grade and high-grade trochlear dysplasia, respectively. All calculations were statistically significant (p < 0.05).

CONCLUSION

The knee rotation angle might meet the requirements for precise diagnostics in knee realignment surgery. Unlike TT-TG, this parameter seems not to be affected by a dysplastic trochlea. In addition, the dimensionless parameter is independent of the knee size of the individual.

LEVEL OF EVIDENCE

II.

3D CAD/reverse engineering technique for assessment of Thai morphology: Proximal femur and acetabulum

PURPOSE

To assess morphological parameters of proximal femur and acetabulum in Thai population with three-dimensional measurement technique, and to analysis of collateral side symmetric, gender difference, and correlation between morphometric parameters.

METHODS

Investigation was performed in 240 femurs. All three-dimensional femur models were acquitted from 64-slice spiral CT scanner. Morphometric parameters under consideration included acetabular diameter, femoral head diameter, shaft isthmus location, intramedullary canal diameter, diaphyseal diameter, femoral head height, femoral neck isthmus, femoral neck length, neck shaft angle, bow angle, and anteversion angle. All parameters were measured based on functions and least-square regression function in CAD software. Obtained measured data were then used for analysis of collateral side symmetric, gender difference, correlation between morphometric parameters, and compared with other populations.

RESULTS

Female had a smaller dimension compared with male in most of the parameters. No significant difference was observed between left and right femurs. High correlation pairs of morphometric parameters included femoral head diameter-acetabular diameter, femoral head diameter-neck isthmus diameter, femoral head diameter-diaphyseal diameter at shaft isthmus level, acetabular diameter-neck isthmus diameter, neck isthmus diameter-diaphyseal diameter at shaft isthmus level, and acetabular diameter-diaphyseal diameter at shaft isthmus level. Some morphometric parameters of Thai are smaller than other Caucasian, and some Asian nation, i.e. femoral head diameter, femoral neck length, and femoral head height.

CONCLUSIONS

This study provides essential morphometric data for various orthopedic implant designs relating to proximal femur region.

PATELLOFEMORAL ARTHROPLASTY CHANGES THE TROCHLEAR GROOVE ANGLE

High early failure rates occur in the treatment of isolated symptomatic patellofemoral arthritis with commercially available patellofemoral arthroplasty (PFA) prostheses. We postulate that PFA changes the trochlear groove angle, thereby causing patellar maltracking, catching and pain. We examined the extent of this change in trochlear groove angle by virtually implanting five commercially available patellofemoral prostheses into two 3D reconstructed knees, one with a normal and the other with a dysplastic trochlea. The axial and coronal trochlear groove angles were measured pre- and post PFA for the five different prostheses in both the normal and the dysplastic knee. Post PFA, the trochlear groove angle changed from the original in both the axial and coronal planes for all the prostheses in both the normal and the dysplastic knee. The trochlear groove change is dependent on the design of the specific prosthesis. To avoid excessive changes post PFA, both the wide variation of changes between different generic PFA prostheses, as well as the wide variation in patient femoral anatomy should be considered.

The patellofemoral joint: from dysplasia to dislocation

Patellofemoral dysplasia is a major predisposing factor for instability of the patellofemoral joint. However, there is no consensus as to whether patellofemoral dysplasia is genetic in origin, caused by imbalanced forces producing maltracking and remodelling of the trochlea during infancy and growth, or due to other unknown and unexplored factors.The biomechanical effects of patellofemoral dysplasia on patellar stability and on surgical procedures have not been fully investigated. Also, different anatomical and demographic risk factors have been suggested, in an attempt to identify the recurrent dislocators. Therefore, a comprehensive evaluation of all the radiographic, MRI and CT parameters can help the clinician to assess patients with primary and recurrent patellar dislocation and guide management.Patellofemoral dysplasia still represents an extremely challenging condition to manage. Its controversial aetiology and its complex biomechanical behaviour continue to pose more questions than answers to the research community, which reflects the lack of universally accepted guidelines for the correct treatment. However, due to the complexity of this condition, an extremely personalised approach should be reserved for each patient, in considering and addressing the anatomical abnormalities responsible for the symptoms. Cite this article: EFORT Open Rev 2017;2. DOI: 10.1302/2058-5241.2.160081. Originally published online at www.efortopenreviews.org.

Patient's Height and Hip Medial Offset Are the Main Determinants of the Valgus Cut Angle During Total Knee Arthroplasty

BACKGROUND

Valgus cut angle (VCA), defined as the angle between the anatomical and the mechanical axes of femur, is an important parameter upon which a critical step of knee arthroplasty is based. Some variables have been proposed to affect the magnitude of this cut. However, little information is available regarding whether a generic value can be used, or if a patient-specific value from a long leg X-ray, or factors that can be determined preoperatively, is necessary to accurately set the VCA.

METHODS

Standard standing 3-joint views were used to measure a number of anatomical measurements in 358 limbs, 202 patients (116 women, 86 men). Neck-shaft angle, medial offset, femoral length (FL), distal femoral articular angle, and VCA were measured. Demographic data including gender and height were extracted from hospital charts. The correlation of VCA with each of the other factors was evaluated using linear regression and t-test and finally multivariate analysis.

RESULTS

The average VCA was 5.76° (range 4-8). Gender and distal femoral articular angle were not related to VCA (P = .343 and .995). FL was found to be a function of height with similar effects on multivariate analysis. Only the height (or FL) and femoral offset were identified as independent factors, with a negative correlation for the former (P < .001) and a positive correlation for the latter (P < .001).

CONCLUSION

Femoral offset and height are the 2 independent factors determining VCA. Other parameters are indirectly related to these 2 factors. Tall patients with a small femoral offset have smaller VCA and short patients with a large offset have larger VCA. The wide variety of VCA values does not support using a generic value for all patients during knee arthroplasty.

Increased Femoral Anteversion Influence Over Surgically Treated Recurrent Patellar Instability Patients

PURPOSE

To verify the influence that increased femoral anteversion (FA) has on patients with recurrent patellar instability (RPI) treated by anteromedialization tibial tubercle osteotomy (TTO) combined with medial patellofemoral ligament reconstruction (MPFLR) and to present the midterm outcomes of these patients.

METHODS

From January 2008 to August 2013, skeletally mature patients with RPI and tibial tubercle (TT)-trochlear groove (TG) ≥ 17 mm who underwent anteromedialization TTO combined with MPFLR were evaluated for J sign, patellar glide, apprehension test, increased FA, Caton index, trochlea dysplasia, TT-TG, Kujala, International Knee Documentation Committee subjective knee evaluation form, and Tegner. Increased FA was determined clinically by a difference of more than 30° between hip internal and external rotation, 70° or more of hip internal rotation, and 30° or more of femoral neck anteversion. A subgroup analysis involving increased FA was made.

RESULTS

Forty-eight patients composed the study group. Mean follow-up was 41.5 ± 11.05 months. The J-sign was present in 86% before surgery and none postoperatively (P < .001). All patients had a positive apprehension test or a patellar luxation at the patellar glide test rated as grade 4 before surgery. After surgery, the mean glide was 1.29 ± 0.45 with no apprehension (P < .001). Increased FA was present in 18.7%. Caton index before surgery was 1.11 ± 0.21 and 0.99 ± 0.11 postoperatively (P = .004). Trochlea dysplasia was present in all patients. TT-TG preoperatively was 20.77 ± 2.12 mm and 11.33 ± 1.24 mm postoperatively (P < .001). Functional scores improved preoperatively to postoperatively (P < .001) with Kujala and International Knee Documentation Committee means: 59.08 to 84.37; 52.6 to 85.5, respectively. Tegner preinjury score was 5.4 and postoperatively was 5.2 (P = .01). Increased FA group had worse Kujala compared with the normal FA group and worse Kujala improvement: 77.7 and 85.89 (P = .012), and 21.7 and 26.1, respectively (P < .001).

CONCLUSIONS

Increased FA in patients with RPI had a negative effect on the outcome of anteromedialization TTO combined with MPFLR. Combined anteromedialization TTO and MPFLR had good functional midterm outcomes in treating patients with RPI and TT-TG ≥ 17 mm.

LEVEL OF EVIDENCE

Level III, comparative study.

A Validated Single-View Radiographic Alternative to Computed Tomography for the Measurement of Femoral Anteversion: A Method-Comparison Study

BACKGROUND

Although preoperative templating in total hip arthroplasty is helpful to ensure appropriate component position, there is no single-view radiographic method to determine femoral anteversion (FA) preoperatively. The aim of the present study was to validate the use of radiographic measurement of FA using a modified Budin view.

METHODS

This prospective study reports on 105 limbs from 65 patients. Computed tomography (CT) scans and radiographs were obtained to measure native FA. Radiographs were obtained using the modified Budin protocol with 90° flexion at the knee and 90° flexion and 30° abduction at the hip. Pearson correlation analyses, paired-samples t-test, and Bland-Altman plots were performed to assess correlation and agreement between methods. Data were grouped into subsets based on CT-derived FA in 5° intervals. Groups included all limbs, FA < 35°, FA < 30°, and FA < 25°.

RESULTS

For all limbs, Bland-Altman analysis revealed a fixed bias (mean bias, -0.8°; 95% confidence interval, -1.4° to -0.2°) and showed that radiographic methods underestimated FA. Subset analyses were performed and revealed excellent correlation between CT and radiographic measurements for all subgroups (r = 0.97, P < .001). Paired-samples t-tests revealed no significant difference between methodologies for any of the subgroups. Radiographic and CT methods showed excellent agreement, and the bias between methods was within 0.5° for all subgroups. There was no fixed bias and thus no systematic difference in methods within any of the subgroup analyses.

CONCLUSION

Radiographic measurement of FA using a modified Budin view is a valid and reliable technique.

Patient-specific modeling of the trochlear morphologic anomalies by means of hyperbolic paraboloids

Diagnostic and therapeutic purposes are issuing pressing demands to improve the evaluation of the dysplasia condition of the femoral trochlea. The traditional clinical assessment of the dysplasia, based on Dejour classification, recognized 4 increasing (A, B, C, D) levels of severity. It has been extensively questioned in the literature that this classification methodology can be defective suggesting that quantitative measures can ensure more reliable criteria for the dysplasia severity assessment. This study reports on a novel technique to model the trochlear surface (TS), digitally reconstructed by 3D volumetric imaging, using three hyperbolic paraboloids (HP), one to describe the global trochlear aspect, two to represent the local aspects of the medial and lateral compartments, respectively. Results on a cohort of 43 patients, affected by aspecific anterior knee pain, demonstrate the consistency of the estimated model parameters with the morphologic aspect of the TS. The obtained small fitting error (on average lower than 0.80 mm) demonstrated that the ventral aspect of the trochlear morphology can be modeled with high accuracy by HPs. We also showed that HP modeling provides a continuous representation of morphologic variations in shape parameter space while we found that similar morphologic anomalies of the trochlear aspect are actually attributed to different severity grades in the Dejour classification. This finding is in agreement with recent works in the literature reporting that morphometric parameters can only optimistically be used to discriminate between the Grade A and the remaining three grades. In conclusion, we can assert that the proposed methodology is a further step toward modeling of anatomical surfaces that can be used to quantify deviations to normality on a patient-specific basis.

High Femoral Anteversion Is Related to Femoral Trochlea Dysplasia

PURPOSE

To investigate the possible relation between femoral anteversion (AV) and trochlear morphology.

METHODS

Among 560 available lower-limb computed tomography (CT) scans, those with previous fracture, arthroplasty, or osteotomy were excluded and 40 cases were randomly selected. The following 4 lines were determined from the CT scans: 1 through the center of the femoral head and neck; 1 through the lesser trochanter and the center of the femoral shaft; 1 as a tangent to the dorsal part of the distal femur, just above the gastrocnemius insertion; and 1 as a tangent to the posterior condyles. Between the respective lines, the following parameters of femoral AV were determined: (1) total AV, (2) proximal AV, (3) diaphyseal AV, and (4) distal AV. Trochlea parameters were determined from 2 separate axial CT slices (proximal trochlea and 5 mm farther distally): trochlea height (medial, central, lateral), transverse trochlea shift, trochlea depth, sulcus angle, lateral trochlea slope, and Dejour trochlea type. To prove or disprove our study hypothesis, a correlation analysis was performed between the variables of AV and trochlear morphology.

RESULTS

The total AV was significantly correlated with the trochlea parameters trochlea depth (P = .032), sulcus angle (P = .05), and lateral trochlea slope (P = .001). The diaphyseal AV was significantly correlated with the sulcus angle (P = .009). The distal AV showed significant correlations with medial, central, and lateral trochlea height (.005 <P < .032) and with Dejour trochlea type (P = .043).

CONCLUSIONS

The morphology of the trochlea is significantly related to femoral AV. Increased AV is associated with a flatter, more dysplastic trochlea. This was particularly true for AV located at the distal femur.

LEVEL OF EVIDENCE

Level III, diagnostic study of nonconsecutive patients.

Femoral version, neck-shaft angle, and acetabular anteversion in Chinese Han population: a retrospective analysis of 466 healthy adults

Anatomic data regarding femoral version, neck-shaft angle, and acetabular anteversion are still limited in Chinese Han adult population. The aim of this study was to investigate the effects of age, sex, and body laterality on the 3 important anatomic indicators in Chinese Han healthy adults. Measurements were performed independently by 3 experienced observers using the picture archiving and communication system (PACS) in healthy adults who had received imaging tests of the femur and acetabulum between January 2009 and October 2014. Relevant data were measured and analyzed. A total of 466 adults (353 males and 113 females) were included. The mean femoral version, neck-shaft angle, and acetabular anteversion for all were 10.62, 133.02, and18.79, respectively. Age-based analysis showed that adults younger than 60 years had a significantly higher neck-shaft angle (P < 0.001) but a significantly lower acetabular anteversion (P < 0.001) than those older than 60 years. Sex-based analysis revealed that females had significantly higher values of femoral version (P < 0.001) and acetabular anteversion (P < 0.001) than males. Laterality-based analysis found the left side had a significantly lower acetabular anteversion (P < 0.001) than the right side. Outcomes of multiple linear regression analysis indicated that femoral version may be associated with sex (P < 0.001) but not age (P = 0.076) or laterality (P = 0.430), neck-shaft angle may be associated with age (P < 0.001) but not sex (P = 0.378) or laterality (P = 0.233), and acetabular anteversion may be associated with age (P < 0.001) and sex (P < 0.001) but not laterality (P = 0.060). In this representative Chinese cohort, neck-shaft angle may decrease, whereas acetabular anteversion may increase with age, females may have higher values of femoral version and acetabular anteversion than males, and the right body side may have a higher value of acetabular anteversion than the left side.