Proximal external femoral torsion increases lateral femoral shaft bowing: a study based on 3D CT reconstruction models.

PURPOSE: Femoral bowing influences the genesis and management of knee osteoarthritis (OA). The aim of this study was to investigate the relationship between the femoral torsion angle (FTA) and femoral bowing angle (FBA) in a southern Chinese population. It was hypothesized that a greater FTA would lead to a greater lateral FBA. METHODS: A total of 381 lower extremities from 381 osteoarthritic patients (298 women, 83 men; 201 left, 180 right; mean age 66.5 ± 8.9 years) were retrospectively reviewed. Age, sex, body mass index (BMI), side, height, femoral length (FL), hip-knee-ankle angle (HKA) and FTA were set as FBA-related factors. The three-dimensional (3D) FBA, the angle between the anatomical axis of the proximal femur and the anatomical axis of the distal femur in the plane they form, and its projection on the coronal (lateral FBA) and sagittal (anterior FBA) planes were measured on 3D computed tomography (CT) models. The correlation of the 3D, lateral and anterior FBAs with each of the FBA-related factors was explored using multiple linear regression analysis. The correlation between the FBA and FTA was explored and verified after using propensity score matching to control for the other FBA-related factors. RESULTS: The mean lateral and anterior FBAs were 5.5°, with 53.5% greater than 5°, and 12.7°, with 70.3% greater than 11°, respectively. 3D FBA was positively correlated with age (Std.Co = 0.113, P < 0.05) and HKA (Std.Co = 0.129, P < 0.05). Lateral FBA was positively correlated with age (Std.Co = 0.118, P < 0.05), female sex (Std.Co = 0.206, P < 0.05), HKA (Std.Co = 0.184, P < 0.05) and FL (Std.Co = 0.220, P < 0.05). Anterior FBA was positively correlated with age (Std.Co = 0.108, P < 0.05) and male sex (Std.Co = 0.108, P < 0.05). When the related factors were balanced between the two groups (NS), FTA did not significantly affect 3D FBA or anterior FBA (NS), while FTA was positively correlated with lateral FBA (Std.Co = 0.165, P < 0.05). CONCLUSION: External torsion of the proximal femur increases the lateral FBA by twisting a partial anterior FBA into a lateral FBA, especially in the female population. If a patient is found to have a large lateral FBA preoperatively, one should be alert to the possibility of a concomitant large FTA, as there are implications for femoral orthopedics, TKA and patellofemoral pressure distribution. LEVEL OF EVIDENCE: III.

Risk Factors Associated with Intraoperative Iatrogenic Fracture in Patients Undergoing Intramedullary Nailing for Atypical Femoral Fractures with Marked Anterior and Lateral Bowing.

Background and objectives: Iatrogenic fractures are potential complications during intramedullary (IM) nailing for atypical femoral fractures (AFFs). The risk factors associated with iatrogenic fractures remain unclear, although excessive femoral bowing and osteoporosis are hypothesized to be contributing factors. The present study aimed to determine the risk factors for the occurrence of iatrogenic fractures during IM nailing in patients with AFFs. Materials and Methods: This retrospective cross-sectional study evaluated 95 patients with AFF (all female; age range: 49-87 years) who underwent IM nailing between June 2008 and December 2017. The patients were divided into two groups: Group I (with iatrogenic fracture: n = 20) and Group II (without iatrogenic fracture: n = 75). Background characteristics were retrieved from medical records and radiographic measurements were obtained. Univariate and multivariate logistic regression analyses were performed to identify risk factors for the occurrence of intraoperative iatrogenic fractures. Receiver operating curve (ROC) analysis was conducted to determine a cut-off value for the prediction of iatrogenic fracture occurrence. Results: Iatrogenic fractures occurred in 20 (21.1%) patients. The two groups exhibited no significant differences regarding age and other background characteristics. Group I exhibited significantly lower mean femoral bone mineral density (BMD) and significantly greater mean lateral and anterior femoral bowing angles than Group II (all p < 0.05). There were no significant differences in AFF location, nonunion, and IM nail diameter, length, or nail entry point between the two groups. In the univariate analysis, femoral BMD and lateral bowing of the femur differed significantly between the two groups. On multivariate analysis, only lateral bowing of the femur remained significantly associated with iatrogenic fracture occurrence. The ROC analysis determined a cut-off value of 9.3° in lateral bowing of the femur for prediction of iatrogenic fracture occurrence during IM nailing for AFF treatment. Conclusions: The lateral bowing angle of the femur is an important predictive factor for intraoperative iatrogenic fracture occurrence in patients undergoing IM nailing for AFF treatment.

Total knee arthroplasty in femoral bowing: does patient specific instrumentation have something to add? A randomized controlled trial.

BACKGROUND: Patient-specific instrumentation (PSI) proponents have suggested the benefits of improved component alignment and reduced outliers. In this randomized controlled trial, we attempted to assess the advantage of using PSI over conventional intermedullary (IM) guides for primary total knee arthroplasty (TKA) with bilateral severe femoral bowing (> 5°). A parallel trial design was used with 1:1 allocation. We hypothesize that PSI would support more accurate alignment of components and the lower-limb axis during TKA with severe femoral bowing in comparison with conventional IM guides. METHODS: Among 336 patients undergoing bilateral TKAs due to knee osteoarthritis, 29 patients with bilateral lateral femoral bowing of more than 5° were included in this study. Every patient was assigned randomly to PSI on one side and to conventional instrumentation lateralization of the entry point of the femoral IM guide was applied on the other with a goal of neutral mechanical alignment. The assessment of coronal alignment was completed by measuring the hip-knee-ankle (HKA) angle on preoperative and postoperative long film standing radiographs. Coronal and sagittal orientations of femoral and tibial components were assessed on weight-bearing radiographs. The rotational alignment of the femoral component was evaluated using computed tomography. RESULTS: The postoperative mean ± standard deviation (SD) HKA angle was varus 4.0° (± 2.7°) for conventional technique and varus 4.1° (± 3.1°) for PSI, with no differences between the two groups (p = 0.459). The component orientation showed no significant differences except with respect to the sagittal alignment of the femoral component (p = 0.001), with a PSI mean ± SD flexion of 5.8° (± 3.7°) and a conventional method mean ± SD flexion of 3.2° (± 2.5°), due to the intentional 3° flexion incorporated in the sagittal plane to prevent femoral notching in PSI planning. Computed tomography assessment for rotational alignment of the femoral components showed no difference between the two groups concerning the transepicondylar axis (p = 0.485) with a PSI mean ± SD external rotation of 1.5° (± 1.3°) and conventional mean ± SD external rotation of 1.5° (± 1.6°). CONCLUSION: PSI showed no advantage over lateralization of the femoral entry for IM guidance. LEVEL OF EVIDENCE: 1 TRIAL REGISTRATION: Registered on US national library of medicine ClinicalTrials.gov ( NCT02993016 ) on December 12th 2016.

Straight nail insertion through a laterally shifted entry for diaphyseal atypical femoral fractures with bowing: good indications and limitations of this technique.

PURPOSE: Inserting a straight (piriformis fossa entry) nail through the tip of the greater trochanter has been used for treating atypical femoral fractures (AFFs) with bowing. This study aimed to determine what degree of bowing can be successfully treated using a laterally shifted entry technique. METHODS: Twenty-three complete and six incomplete diaphyseal AFFs treated using the shifted entry technique were retrospectively analysed. Radiologic parameters and complications were evaluated. The complete AFFs were divided into two groups based on the severity of preoperative bowing: grade 0-II bowing and < 20° lateral bowing (minimal/moderate) and grade III bowing or ≥ 20° lateral bowing (severe). Comparison according to postoperative malalignment, a change of lateral or anterior bowing ≥ 5° was also performed. RESULTS: Three complete AFFs in the minimal/moderate group showed malalignment, as did all in the severe group (p < 0.001). The change of bowing was greater for the severe group in lateral and anterior bowing (p = 0.004 and 0.001, respectively). A greater fracture gap was found on AP and lateral radiographs in the severe group (p = 0.044 and 0.026, respectively). In the comparison according to postoperative malalignment, a significant difference was found for the percentage of severe deformity (p < 0.001). All incomplete AFFs were united without complication. CONCLUSION: Diaphyseal AFFs with grade 0-II bowing and < 20° anterior bowing were treated successfully by the shifted entry technique. However, postoperative malalignment was found in all cases of AFFs with severe bowing. Therefore, other techniques should be considered for AFFs with grade III bowing or ≥ 20° anterior bowing.

Clinical outcomes of using contralateral-side laterally bent intramedullary nails in atypical femur fractures with femoral bowing.

INTRODUCTION: This study aimed to evaluate the clinical outcomes of using contralateral-side laterally bent intramedullary nails (IMNs) in bowed atypical femur fractures (AFFs). MATERIALS AND METHODS: We retrospectively reviewed bowed AFFs treated with contralateral-side laterally bent IMNs. In total, 20 patients with 25 cases of AFFs were included. Surgical outcomes including bone union time, complications, femoral bowing, and leg length discrepancy (LLD) were evaluated. We evaluated the surgical safety of performing contralateral-side intramedullary nailing with its intraoperative and postoperative complications and compared the LLD. RESULTS: The average age was 76.8 years (range 67-86 years), and all of patients were female. There were 10 cases of complete AFFs and 15 cases of incomplete AFFs. Fourteen patients (70%) had a history of bisphosphonate (BP) use with an average of 74.5 months of its use. In the complete AFF cases, reduction of the fractures was tried to restore the patients' normal anatomical geometry. The average lateral gap was 0.6 mm (0-1 mm), and the average medial gap was 1.6 mm (1-3 mm). All cases achieved bone union without secondary intervention. There were no intraoperative fractures or postoperative complications. The average bone union time was 22.0 weeks and 9.2 weeks in complete and incomplete AFFs, respectively. The average preoperative femoral bowing seen in the coronal and sagittal planes was 10.1° and 16.1°, respectively, while the average postoperative bowing was 6.6° and 11.3°, respectively. The average change of angle was 3.5° in the coronal plane and 4.8° in the sagittal plane. The mean change of LLD was 5.7 mm. CONCLUSION: The use of contralateral-side laterally bent IMNs in treating bowed femurs showed excellent clinical outcomes without complications. In severely bowed femurs, this technique can be safe and useful.

Slight under-correction using individualized intentional varus femoral cutting leads to favorable outcomes in patients with lateral femoral bowing and varus knee.

PURPOSE: Restoration of neutral alignment is considered key in total knee arthroplasty (TKA). However, this may be undesirable and can result in medial soft-tissue over-release in patients with varus knee and lateral femoral bowing. This study aimed to determine whether individualized intentional varus distal femoral cutting yielded satisfactory clinical and radiological outcomes. METHODS: A total of 77 patients (91 knees) with varus knee (hip-knee-ankle axis ≥ 10°) and lateral femoral bowing > 5° underwent navigation-assisted primary TKA using individualized intentional varus distal femoral cutting. Knee Society scores, Western Ontario and McMaster Universities scores, and radiographs for limb alignment, implant alignment, and aseptic loosening were evaluated. Subgroup analyses were performed according to the limb alignment and coronal femoral component alignment (0° ± 3° vs. varus of > 3°). RESULTS: All clinical outcomes significantly improved at the final follow-up (p < 0.05 in all). The mechanical axis angle changed from 13.1° ± 2.7° to 2.8° ± 1.5°. The coronal femoral component angle at the final follow-up was 2.8° ± 1.3°. Radiolucent lines were observed in 6 cases (6.6%) and were less than 2 mm in all cases without progression. In subgroup analyses, no significant differences were observed in clinical outcomes (n.s. in all) and in the incidence of radiolucent lines (n.s. in limb alignment, n.s. in coronal femoral component alignment). CONCLUSIONS: Individualized intentional varus distal femoral cutting yielded favorable clinical outcomes without complications at 5-year follow-up. Slight under-correction using intentional varus distal femoral cutting could be a viable option in patients with varus knee and lateral femoral bowing during navigation-assisted TKA. LEVEL OF EVIDENCE: IV.

Does patient-specific instrumentation increase the risk of notching in the anterior femoral cortex in total knee arthroplasty? A comparative prospective trial.

PURPOSE: Patient-specific instrumentation (PSI) was usually applied in total knee arthroplasty (TKA) to acquire a favourable alignment. We hypothesized that using PSI had a potential risk of notching in the anterior femoral cortex, because the femoral component may be placed in an overextension position due to the distal femoral sagittal anteversion. The aim of this study was to figure out the relationship between the notch and the distal femoral sagittal anteversion in PSI-assisted TKA. METHODS: One hundred thirty-one patients who were to undergo total knee arthroplasty (TKA) were randomly divided into conventional instrumentation (CI) group and PSI group. The computed tomography (CT) data of lower extremities was collected and imported to the Mimics software to reconstruct the three-dimensional (3D) bone image of the femur. The angle between distal femoral anatomic axis (DFAA) and femoral mechanical axis (FMA) on sagittal plane was defined as distal femoral sagittal anteverted angle (DFSAA) and measured. The number of notch intra-operative and post-operative was recorded. Then, we calculated the incidence of the notch and analyzed its relationship with DFSAA. RESULTS: The average DFSAA of 262 femurs is 2.5° ± 1.5° (range, 0.0°-5.7°). When DFSAA ≥ 3°, the incidence of notch was 7.10% in CI group and 33.30% in PSI group, respectively, which shows significant statistical difference in the two groups (P = 0.016 < 0.05). When DFSAA < 3°, the incidence of notch was 6.50% in CI group and 5.30% in PSI group, respectively, which shows no significant statistical difference in the two groups (P = 0.667 > 0.05). CONCLUSION: DFSAA could be taken as an indicator to predict the notch when performing TKA assisted with PSI. Especially when the DFSAA ≥ 3°, the risk of notch could be markedly increased.

In Asian women undergoing total knee arthroplasty, lower leg morphology in those with rheumatoid arthritis differed from those with osteoarthritis.

Objectives: This retrospective, single-center study aimed to compare leg morphology between patients with rheumatoid arthritis (RA) and those with osteoarthritis (OA) undergoing total knee arthroplasty (TKA).Methods: We enrolled 70 RA and 327 OA female patients undergoing TKA. Hip-knee-ankle angle (HKA), femorotibial angle (FTA), valgus correction angle (VCA), and femoral/tibial bowing were measured using full-length radiographs. Femoral bowing of more than 3° or tibial bowing more than 2°, either laterally or medially, was considered substantial. Distribution of these results and the incidence of substantial bowing in RA and OA were compared.Results: HKA, FTA, and VCA were significantly smaller in RA than those in OA. Femoral bowing was significantly smaller in RA (mean angle: 0.04° ± 3.1°) than that in OA (mean angle: 2.1° ± 3.6°) (p < .05). In almost half of the patients with RA (48.6%), femoral bowing occurred medially, whereas femoral bowing occurred laterally in approximately three quarters of OA patients (73.1%). Tibial bowing did not differ. The incidence of substantial femoral bowing was significantly lower in RA (27.1%) than that in OA (43.0%) (p < .05).Conclusion: RA patients undergoing TKA had different leg morphology than OA patients. These findings have implications for surgical planning.

The Role of Lower-Limb Geometry in the Pathophysiology of Atypical Femoral Fracture.

PURPOSEOF REVIEW: The etiology of atypical femoral fracture (AFF) is likely multifactorial. In this review, we examined the recent literature investigating the role of lower-limb geometry in the pathophysiology of AFF. RECENT FINDINGS: Increased femoral bowing was associated with prevalent AFF and a greater likelihood of a diaphyseal versus a subtrochanteric AFF location. Femoral neck geometry or hip alignment may also be related to AFF, but findings remain equivocal. Differences in femoral geometry may, in part, be responsible for the high rate of AFF in Asian compared with Caucasian populations. Finally, simulation studies suggest that lower-limb geometry influences AFF risk via its effects on mechanical strain of the lateral femoral cortex. Femoral geometry, and bowing in particular, is related to prevalent AFF, but more prospective investigation is needed to determine whether measurements of geometry can be used for clinical risk stratification.

Variation of three-dimensional femoral bowing and its relation to physical status and bone mineral density: a study with CT.

PURPOSE: Anatomically, the femoral bone shows sagittal and coronal bowing. Pronounced bowing would affect femoral implant surgery accuracy, but factors associated with degrees of three-dimensional (3D) femoral bowing have not yet been identified. This study measured 3D femoral bowing and examined the correlation between 3D femoral bowing and risk factors. METHODS: 3D femoral bone models of unaffected legs from 125 patients were reconstructed from computed tomography data. A trans-epicondylar axis (TEA)-based coordinate system was introduced into bone models and the reproducibility of this coordinate system was evaluated. The cross-sectional contours of the femoral canal were extracted along the vertical axis of the TEA-based coordinate system, and the angles of 3D femoral bowing were examined. RESULTS: The reproducibility to set the coordinate was very high. Total, sagittal, and coronal femoral bowing were 8.9 ± 1.8°, 8.7 ± 1.8°, and 0.1 ± 1.9°, respectively. There was no significant difference in the degrees of femoral bowing between males and females. Total, coronal, and sagittal femoral bowing correlated with age, height, and femoral length, but only femoral coronal bowing correlated with bone mineral density (BMD) of the femur and lumbar spine. CONCLUSIONS: We introduced a highly reproducible method for measuring femoral sagittal and coronal bowing by constructing a femoral 3D coordinate system. Anterior femoral bowing was the dominant direction of bowing in our Japanese cohort, whereas the degree of lateral bowing correlated with age, height, femoral length, and BMD. Our results suggest that lateral femoral bowing could increase with aging and decreasing BMD.

Influence of femoral bowing on range of motion after total hip arthroplasty.

PURPOSE: The influence of physiologic femoral bowing on range of motion (ROM) after total hip arthroplasty (THA) remains unknown. The purpose of this study was to investigate the morphology of the femur in patients who underwent THA, and to analyze the influence of femoral bowing on ROM due to implant impingement after THA. METHODS: The ROM was calculated from 100 hips in 90 patients who underwent THA using computed tomography data with a 3D dynamic analysis software. Lateral and anterior bowing angles of the femur were measured. A modular implant (Modulus system, Lima Corporate, Villanova di San Daniele del Friuli, Italy) was used for simulation. In all subjects, cup inclination, anteversion, and stem anteversion were set to 40°, 15°, and 30°, respectively. Multiple linear regression analyses were performed to assess the relationship between the morphology of the femur and ROM. RESULTS: Lateral bowing of the femur was demonstrated to be significantly correlated with age (r = 0.361, p < 0.001) and female sex (r = 0.315, p = 0.001). Lateral bowing of the femur was significantly positively correlated with flexion and internal rotation (Int-R) with 90° flexion. Anterior bowing was significantly associated with decreasing flexion, decreasing Int-R with 90° flexion and increasing Int-R with 45° flexion and 15° adduction. CONCLUSIONS: A ROM-optimized cup position cannot be calculated from femoral stem anteversion values alone; therefore, when surgeons position the cup in relation to the femoral stem anteversion, the influence of femoral bowing may also require consideration.

Surgical outcomes of intramedullary nailing for diaphyseal atypical femur fractures: is it safe to modify a nail entry in bowed femur?

INTRODUCTION: The purpose of the study was to determine the surgical outcomes of intramedullary nailing in diaphyseal atypical femoral fractures (AFFs) and to evaluate the clinical outcomes of nail entry modification technique. MATERIALS AND METHODS: We retrospectively reviewed diaphyseal AFFs treated with IMN at nine institutions. In total, 82 patients were included. Surgical outcomes such as complication, union time, and femoral bowing were evaluated. We modified the nail entry of the straight nail from piriformis fossa to the tip of the greater trochanter in the bowed femur and compared the surgical outcomes between the original group and the modification group. RESULTS: The average union time was 20.1 weeks, and the union rate was 89.0%. The average union time was 13.1 weeks and 21 weeks in incomplete and complete AFFs, respectively. There was no nonunion in incomplete AFFs, but 13.8% in complete AFFs. Complete AFFs had 86.2% of union rate. There were 46 cases of group 1 with original entry point and 19 cases of group 2 with modified entry. In group 2, the union rate was similar to group 1 and union time was shorter. CONCLUSION: Changing the entry point laterally allowed the nail to be accommodated in bowed femurs, decreasing the risk of deformity and improving healing time. In severely varus femur, the lateral entry of the straight nail can be a useful technique.

[Individual difference of coronal bowing of femur and its influence on the lower limbs alignment after the total knee arthroplasty].

Objective: To disclose the correlation between the femur bowing angle(FBA) and vulgas correction angle(VCA), anlysys its influence on the total knee arthroplasty and the lower limbs alignment. Methods: From Janurary 2013 to December 2015, 699 patients who had received total knee arthroplasty(TKA)were collected in the Department of Joint Surgery, China-Japan Friendship. The FBA, VCA, offset of the proximal femur, the lengh of the femur, the neck shaft angle of the femur of the eligible cases from the long leg X-ray were measured.All the data were analysed for the following steps: the FBA's mean value and characteristics of distributation of all the cases; the VCA's mean value and characteristics of distributation of all the cases; correlations between the VCA and the other parameters; divide all the cases into four groups based on the value of FBA : group A(FBA<-3°, 29), group B(-3°≤FBA≤0°, 255), group C(0°3°, 236)and then plan to cut the distal femur with 5° and 6°, respectively. The percent of ideal alignmental outcome's percentage of every group were compared. Results: The mean Value of the FBA is -7.1--12.1(1.4±2.4)°; the mean Value of the VCA is 2.5--11.9(6.5±1.3)°. The correlation index between VCA and FBA, the neck shaft angle of the femur , offset of the hip joint, the lengh of the femur is 0.72, -0.26, 0.45 and -0.08, perspectively. The theoretical ideal alignment percentage of the 5 degree-valgus-bone cut and 6 degree-valgus-bone cut in every group is group A: 89.7% and 66.5%; group B: 93.7% and 95.7%; group C: 71.9% and 94.6%; group D: 21.2% and 50.8%, respectively. Conclusion: The cases whose femur bowing angles are outliers are common in daily medical practice, so the vulgas correction angles need be ajusted for its significant correlation with FBA. 5 degree-valgus-bone cut or 6 degree-valgus-bone cut could not get the ideal alignment some times.

Associations between femoral 3D curvature and sagittal imbalance of spine.

Background: The sagittal imbalance (SI) of spine triggers compensatory mechanisms (CMs) of lower extremity (LE) to restore trunk balance. These CMs can cause long-period stress on the femur and may possibly alter the femoral morphology. This cross-sectional observational study aimed to answer the following questions: (a) Do SI subjects exhibit greater femoral bowing compared to subjects with sagittal balance? (b) Are there associations between femoral bowing and CMs of LE in SI subjects? Methods: Subjects who underwent biplanar full body radiographs with the EOS imaging system between January 2016 and September 2021 were recruited. Sagittal parameters included T1-pelvic angle (TPA), pelvic incidence (PI), pelvic tilt (PT), sacral slope, lumbar lordosis (LL), PI-LL, and PT/PI ratio. LE parameters were femoral obliquity angle (FOA), knee flexion angle (KA), and ankle dorsiflexion angle. Femoral bowing was quantified as 3D radius of femoral curvature (RFC). Associations between 3D RFC and the radiographic parameters were analyzed. Results: A total of 105 subjects were included, classified into balance group (TPA < 14°, n = 40), SI group (TPA ≥ 14° and KA <5°, n = 30), and SI with knee flexion group (TPA ≥ 14° and KA ≥ 5°, n = 35). 3D RFC was significantly lower in SI with knee flexion group compared to the other two groups (both p < 0.001). Stepwise linear regression showed that age, SI and knee flexion, femoral length (FL), FOA, and KA were independent predictors for 3D RFC. Conclusion: Greater femoral bowing is observed in subjects with SI and knee flexion compared to the balanced population. CM parameters, including KA and FOA, are associated with 3D RFC. Further longitudinal study is needed to investigate the cause-and-effect relationship between SI, CMs of LE, and femoral bowing.

No single safe zone exists for the valgus cut angle to reproduce neutral mechanical alignment in the presence of femoral bowing in total knee arthroplasty.

PURPOSE: The aim of this study is to report the prevalence of femoral bowing in the Egyptian arthritic knees as a representative of the middle eastern population and to study the correlation between the femoral bowing and the degree of arthritis, varus deformity and the distal femoral valgus cut angle (VCA). METHODS: This is a single-center observational cross-sectional study. Out of 562 knees Scheduled for TKA, 124 knees were excluded leaving 438 knees eligible for the study. The following angles were measured by two independent orthopedic surgeons: Femoral bowing angle (FBA), HKA angle, LDFA, MPTA and VCA. RESULTS: Out of 438 knees, 21knees (4.8%) had medial bowing (< - 3°), 111 (25.3%) had normal bowing (+ 3° to - 3°) and 306 (69.9%) had LFB of which 111 (25.34%) had mild LFB (+ 3 to + 5°) and 195 (44.52%) had severe LFB (> + 5°) bowing. LFB was more in older age group (p = 0.005), in females (p < 0.001), and in grade 4 OA, (p < 0.001). Also, there was a significant positive correlation between FBA and age and increasing varus HKA, and with varus orientation of the distal femur and the tibial plateau. The mean and the 95% confidence interval of the VCA for the medial bowing group was 3.43 (3.01-3.85°), for the normal bowing group was 5.42 (5.15-5.68°), for the mild lateral bowing was 6.74 (6.47-7°), and for the severe bowing group was 9.23 (8.89-9.55°). CONCLUSIONS: There is no single safe zone for the VCA to reproduce postoperative neutral coronal alignment especially in cases of severe lateral femoral bowing in TKA. However, the VCA should be analyzed in term of how much femoral bowing exists. In other words, for each subset of femoral bowing there is a safe zone for the VCA.

Correlation between Femoral Neck Version, Sagittal Femoral Bowing Angle and Sagittal Offset of the Femoral Head from the Distal Femur Axis in an Osteological Collection.

Aim: Radiographic analysis of lower limb alignment is crucial for the planning and evaluation of deformity correction. Assessment in the sagittal plane is often overlooked compared with the coronal plane for a variety of reasons. We aimed to investigate the relationship between the femoral head in the sagittal plane and femoral neck version in the axial plane, and how sagittal femoral bowing angle (sFBA) may contribute. Materials and methods: Twenty-five each of high (1-2 standard deviations above mean), normal (2.5° below to 2.5° above the mean), and low (1-2 standard deviations below the mean) version femurs were randomly selected from an osteological collection database, photographed and measured for sFBA and sagittal offset of femoral head from the distal femur axis. Lines were drawn within the proximal and distal quartiles of the shaft to create sFBA. The offset of the distal quartile line and the femoral head was also measured. High intra- and inter-observer correlations were established. The relationship between parameters was assessed using the Pearson coefficient (r). Results: Sagittal offset of the femoral head from the distal femur axis was found to be highly correlated with sFBA (r = 0.78), and only mildly with femoral neck version (r = 0.52). Sagittal femoral bowing angle and femoral neck version share no relationship (r = 0.05). Conclusions: Neither the sFBA nor sagittal femoral head offset is strongly associated with femoral neck version. Clinical significance: Our data reinforce the need for long leg lateral films to include the femoral head in sagittal deformity analysis, as imaging limited to the knee will not account for the effect of bowing on femoral head position. How to cite this article: Ho D, Liu RW, Mcclure PK. Correlation between Femoral Neck Version, Sagittal Femoral Bowing Angle and Sagittal Offset of the Femoral Head from the Distal Femur Axis in an Osteological Collection. Strategies Trauma Limb Reconstr 2023;18(1):12-15.

Influence of femoral bowing on stress distribution of the proximal femur: a three-dimensional finite element analysis.

BACKGROUND: Whether femoral bowing or its direction has a mechanical effect on the proximal femur is unclear. This study aimed to define the changes in stress distribution in the proximal femur associated with femoral bowing using finite element analysis. METHODS: We created four femoral models: original, entire lateral bowing, entire anterior bowing, and the middle of both (50% anterolateral bowing) from computed tomography data of women with standard bowing. Each model's stress distribution was compared by two-layering the stress distribution under loading conditions during walking. We also evaluated displacement vectors. RESULTS: In all directions of femoral bowing, the stress increased in the femoral neck and the femoral trochanter in the 50% anterolateral bowing. The direction of deformation of the vector for the femoral head increased anteroinferiorly in the 50% anterolateral bowing. CONCLUSIONS: This study showed that the stress distribution at the proximal femur shifted laterally. The high-stress area increased at the femoral neck or trochanter due to increasing femoral bowing. Femoral bowing also increases the anteroinferior vector in the femoral head. This study provides valuable insights into the mechanism of proximal femoral fractures in older adults.

Surgical strategy of the treatment of atypical femoral fractures.

The atypical femoral fracture (AFF) has been attracting significant attention because of its increasing incidence; additionally, its treatment is challenging from biological and mechanical aspects. Although surgery is often required to manage complete AFFs, clear guidelines for the surgical treatment of AFFs are currently sparse. We reviewed and described the surgical treatment of AFFs and the surveillance of the contralateral femur. For complete AFFs, cephalomedullary intramedullary nailing spanning the entire length of the femur can be used. Various surgical techniques to overcome the femoral bowing common in AFFs include a lateral entry point, external rotation of the nail, and the use of a nail with a small radius of curvature, or a contralateral nail. In the case of a narrow medullary canal, severe femoral bowing, or pre-existing implants, plate fixation may be considered as an alternative. For incomplete AFFs, prophylactic fixation depends on several risk factors, such as a subtrochanteric location, presence of a radiolucent line, functional pain, and condition of the contralateral femur; the same surgical principles as those in complete AFFs can be applied. Finally, once AFF is diagnosed, clinicians should recognize the increased risk of contralateral AFFs, and close surveillance of the contralateral femur is recommended.

The accuracy of an extramedullary femoral cutting system in total knee arthroplasty in patients with severe coronal femoral bowing: a radiographic study.

BACKGROUND: Intramedullary (IM) femoral alignment instrument is imprecise for the coronal alignment in total knee arthroplasty (TKA) in patients with severe lateral bowing of the femur, while the extramedullary (EM) alignment system does not depend on the structure of the femoral medullary cavity. The aim of this retrospective study was to compare the accuracy of postoperative limb alignment with the two femoral alignment techniques for patients with severe coronal femoral bowing. METHODS: From January 2017 to December 2019, patients with end-stage knee osteoarthritis and coronal femoral bowing angle (cFBA) ≥ 5° who underwent total knee arthroplasty TKA at our institution were enrolled in the study. The postoperative hip-knee-ankle (HKA) alignment, femoral and tibial component alignment between the IM group and the EM group were compared on 5° ≤ cFBA < 10° and cFBA ≥ 10°. RESULTS: In patients with 5° ≤ cFBA < 10°, no significant differences were observed in the EM group and IM group, including preoperative and postoperative parameters. However, when analyzing the patients with cFBA ≥ 10°, we found a significant difference in postoperative HKA (4.51° in the IM group vs. 2.23°in the EM group, p < 0.001), femoral component alignment angle (86.84° in the IM group vs. 88.46° in the EM group, p = 0.001) and tibial component alignment angle (88.69° in the IM group vs. 89.81° in the EM group, p = 0.003) between the two groups. Compared to the EM group, the IM group presents a higher rate of outliers for the postoperative HKA and femoral components. CONCLUSIONS: The study showed that severe lateral bowing of the femur has an important influence on the postoperative alignment with the IM femoral cutting system. In this case, the application of EM cutting system in TKA will perform accurate distal femoral resection and optimize the alignment of lower limb and the femoral component.

[Effectiveness analysis of lateral condyle sliding osteotomy in total knee arthroplasty for the treatment of lateral femoral bowing deformity].

OBJECTIVE: To investigate the effectiveness of lateral condyle sliding osteotomy (LCSO) in total knee arthroplasty (TKA) for the treatment of lateral femoral bowing deformity. METHODS: The clinical data of 17 patients with lateral femoral bowing deformity treated by LCSO during TKA between July 2018 and July 2020 was retrospectively analysed. There were 3 males and 14 females, with an average of 63.2 years (range, 58-68 years). The etiology of lateral femoral bowing deformity included 12 cases of femoral developmental deformity and 5 cases of femoral fracture malunion. Kellgren-Lawrence classification of knee osteoarthritis was 4 cases of grade Ⅲ and 13 cases of grade Ⅳ. The preoperative hip-knee shaft was 9.5°-12.5° (mean, 10.94°). The disease duration was 3-25 years (mean, 15.1 years). The mechanical lateral distal femur angle (mLDFA), hip-knee-ankle angle (HKA), and mechanical axis deviation (MAD) of the distal femur were measured before operation and at last follow-up to evaluate the correction of extra-articular deformities in the joints and the recovery of mechanical force lines of the lower extremities. The knee society score (KSS) knee score and function score, visual analogue scale (VAS) score, knee joint range of motion (ROM) were used to evaluate effectiveness. The knee varus/valgus stress test and osteotomy healing by X-ray films were performed to evaluate the joint stability and the safety of LCSO. RESULTS: All incisions of the patients healed by first intention after operation, and there was no early postoperative complication such as infection of the incision and deep vein thrombosis of the lower extremities. All 17 patients were followed up 12-36 months, with an average of 23.9 months. The osteotomy slices all achieved bony healing, and the healing time was 2-5 months, with an average of 3.1 months. After operation, the knee varus/valgus stress tests were negative, and there was no relaxation and rupture of the lateral collateral ligament, instability of the knee joint, loosening, revision and infection of the prosthesis occurred. At last follow-up, mLDFA, HKA, MAD, knee ROM, VAS score, KSS knee score and function score significantly improved when compared with preoperative ones ( P<0.05). CONCLUSION: LCSO is effective and safe in TKA with lateral femoral bowing deformity. Extra-articular deformities are corrected intra-articularly. The mechanical force line and joint balance of the lower extremities can be restored simultaneously in an operation.