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Bone & Joint Open
Vol. 2, Issue 12 | Pages 1057 - 1061
1 Dec 2021
Ahmad SS Weinrich L Giebel GM Beyer MR Stöckle U Konrads C

Aims. The aim of this study was to determine the association between knee alignment and the vertical orientation of the femoral neck in relation to the floor. This could be clinically important because changes of femoral neck orientation might alter chondral joint contact zones and joint reaction forces, potentially inducing problems like pain in pre-existing chondral degeneration. Further, the femoral neck orientation influences the ischiofemoral space and a small ischiofemoral distance can lead to impingement. We hypothesized that a valgus knee alignment is associated with a more vertical orientation of the femoral neck in standing position, compared to a varus knee. We further hypothesized that realignment surgery around the knee alters the vertical orientation of the femoral neck. Methods. Long-leg standing radiographs of patients undergoing realignment surgery around the knee were used. The hip-knee-ankle angle (HKA) and the vertical orientation of the femoral neck in relation to the floor were measured, prior to surgery and after osteotomy-site-union. Linear regression was performed to determine the influence of knee alignment on the vertical orientation of the femoral neck. Results. The cohort included 147 patients who underwent knee realignment-surgery. The mean age was 51.5 years (SD 11). Overall, 106 patients underwent a valgisation-osteotomy, while 41 underwent varisation osteotomy. There was a significant association between the orientation of the knee and the coronal neck-orientation. In the varus group, the median orientation of the femoral neck was 46.5° (interquartile range (IQR) 49.7° to 50.0°), while in the valgus group, the orientation was 52.0° (IQR 46.5° to 56.7°; p < 0.001). Linear regression analysis revealed that HKA demonstrated a direct influence on the coronal neck-orientation (β = 0.5 (95% confidence interval (CI) 0.2 to 0.7); p = 0.002). Linear regression also showed that realignment surgery was associated with a significant influence on the change in the coronal femoral neck orientation (β = 5.6 (95% CI 1.5 to 9.8); p = 0.008). Conclusion. Varus or valgus knee alignment is associated with either a more horizontal or a more vertical femoral neck orientation in standing position, respectively. Subsequently, osteotomies around the knee alter the vertical orientation of the femoral neck. These aspects are of importance when planning osteotomies around the knee in order to appreciate the effects on the adjacent hip joint. The concept may be of even more relevance in dysplastic hips. Cite this article: Bone Jt Open 2021;2(12):1057–1061


The Bone & Joint Journal
Vol. 105-B, Issue 2 | Pages 102 - 108
1 Feb 2023
MacDessi SJ Oussedik S Abdel MP Victor J Pagnano MW Haddad FS

Orthopaedic surgeons are currently faced with an overwhelming number of choices surrounding total knee arthroplasty (TKA), not only with the latest technologies and prostheses, but also fundamental decisions on alignment philosophies. From ‘mechanical’ to ‘adjusted mechanical’ to ‘restricted kinematic’ to ‘unrestricted kinematic’ — and how constitutional alignment relates to these — there is potential for ambiguity when thinking about and discussing such concepts. This annotation summarizes the various alignment strategies currently employed in TKA. It provides a clear framework and consistent language that will assist surgeons to compare confidently and contrast the concepts, while also discussing the latest opinions about alignment in TKA. Finally, it provides suggestions for applying consistent nomenclature to future research, especially as we explore the implications of 3D alignment patterns on patient outcomes.

Cite this article: Bone Joint J 2023;105-B(2):102–108.


The Bone & Joint Journal
Vol. 105-B, Issue 2 | Pages 101 - 101
1 Feb 2023
MacDessi SJ Oussedik S Abdel MP Victor J Pagnano MW Haddad FS


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_1 | Pages 224 - 224
1 Jan 2013
Winter A Ferguson K MacMillan J Syme B Holt G
Full Access

The aim of this study is to assess the discrepancy between weight bearing long leg radiographs and supine MRI alignment. There is currently increasing interest in the use of MRI to assess knee alignment and develop custom made cutting blocks utilising this data. However in almost all units MRI scans are performed supine and it is recognised that knee alignment can alter with weight bearing. 46 patients underwent MRI scans as pre-operative planning for Biomet signature total knee replacement and the measure of varus or valgus deformity on MRI was obtained from the plan produced by Biomet Signature software system. 41 of these patients had long leg weight bearing radiographs performed. 33 of these radiographs were amenable to measuring the knee alignment on the picture archiving and communication system (PACS). These measurements were performed by two assessors and inter-observer reliability was satisfactory. There was a significant difference between the alignment as measured on supine MRI compared with weight bearing long leg films. In knee arthroplasty one of the aims is to correct the biomechanical axis of the knee and one of the appeals of custom made cutting blocks is that this can be achieved more easily. However it is important to realise that alignment is not a static value and thus correcting supine alignment may not necessarily result in correction of weight bearing alignment


Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_8 | Pages 32 - 32
1 Apr 2017
Kabariti R Whitehouse M
Full Access

Background. Recent studies have suggested that full-limb radiographs are more accurate and sensitive than short film radiographs for pre-operative measurement of the anatomical angles required to achieve optimal knee alignment in Total Knee Arthroplasty (TKA). However, there are drawbacks associated with their use including excess radiation to the pelvic organs, the need for specialised radiography equipment and increased cost. Given these drawbacks, we compared the use of MRI scans, a commonly performed pre-operative investigation, with short film knee radiographs for measurement of knee alignment. Objective. To investigate whether knee alignment measurements made on MRI scans correlate with those measured on short film knee radiographs in patients with osteoarthritic knees. Methods. We retrospectively reviewed short film knee radiographs and MRI scans of 50 patients with knee osteoarthritis. The plain radiographs had to be performed whilst weight bearing. The MRI scans were performed supine and non-weight bearing. The exclusion criteria included previous trauma to the knee, previous TKA and previous fracture of the lower limb. 4 angle measurements defined by The American Knee Society: alpha, beta, sigma and gamma were measured using each of the 2 modalities. Kolmogorov-Smirnov and two- tailed paired t-tests were used for statistical analysis of the results. Pearson correlation coefficient was used for the measure of dependence. Results. The alpha, beta, sigma and gamma angles obtained using the MR images were different to those obtained using short film weight bearing knee radiographs by −3°± 1° (p < 0.001), 1° ± 3° (p=0.002), 1° ± 3° (p=0.047) and 1° ± 4° (p=0.113) respectively. There was a weak correlation between the MRI based method and the radiographic method in measuring all 4 angles. Conclusions. Our results have shown that the angular measurements performed on MR images should be interpreted with caution as they may vary depending on the MRI slice selected for evaluation. The differences observed and the weak correlation between the 2 modalities may be due to the different scopes used for determining the femoral or tibial axes. The measurements obtained using the plain radiographs were interpreted using a single 2D projection of a 3D structure. However, the measurements of the MR images were evaluated using a 2D image of a slice through a 3D structure. In conclusion, the use of MRI scans for pre-operative planning in TKA may not be advisable at this stage as the angular measurements obtained using the MR images were poorly correlated to those obtained using plain radiographs


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_30 | Pages 42 - 42
1 Aug 2013
Winter A Ferguson K Holt G
Full Access

The aim of this study is to assess the discrepancy between weight bearing long leg radiographs and supine MRI alignment. There is currently increasing interest in the use of MRI to assess knee alignment and develop custom made cutting blocks utilising this data. However in almost all units MRI scans are performed supine and it is recognised that knee alignment can alter with weight bearing. 46 patients underwent MRI scans as pre-operative planning for Biomet signature total knee replacement and the measure of varus or valgus deformity on MRI was obtained from the plan produced by Biomet Signature software system. 41 of these patients had long leg weight bearing radiographs performed. 37 of these radiographs were amenable to measuring the knee alignment on the picture archiving and communication system (PACS). These measurements were performed by two assessors and inter-observer reliability was satisfactory. There was a significant difference between the alignment as measured on supine MRI compared with weight bearing long leg films. In knee arthroplasty one of the aims is to correct the biomechanical axis of the knee and one of the appeals of custom made cutting blocks is that this can be achieved more easily. However it is important to realise that alignment is not a static value and thus correcting supine alignment may not necessarily result in correction of weight bearing alignment


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_9 | Pages 3 - 3
1 Feb 2013
Gbejuade H Hassaballa M Robinson J Porteous A Murray J
Full Access

The gold standard for measuring knee alignment is the lower limb mechanical axis. This is traditionally assessed by weight-bearing full length lower limb X-rays (LLX). CT scanograms (CTS) are however, becoming increasingly popular in view of lower radiation exposure, speed and supine positioning. We assessed the correlation and reproducibility of knee joint coronal alignment using these two imaging modalities. LLX and CTS images were obtained in 24 knees with degenerate joint disease or failed TKR. Hip to ankle mechanical alignment were measured using the PACS software. Coronal knee alignment was assessed from the centre of the knee, measuring the valgus/varus angle relative to the mechanical axis. Measurements were made by two orthopaedic surgeons (Research Fellow and Consultant) on two separate occasions. The mean alignment angles measured by observers 1 and 2 on CTS were 180.29° (SD 6.04) and 180.71° (SD 6.13) respectively, while on LLX were 181.04° (SD7.58) and 181.04° (SD 7.72). The measurements between the two observers were highly correlated for both the CTS (r = 0.97, p < 0.001) and the LLX (r = 0.99, p < 0.001). The angles measured on CTS and LLX were highly correlated (r = 0.826, p < 0.001) with high degree of internal consistency (ICC = 0.804). Malalignment of greater than 5° was seen in 19% of the CTS and 35% of the LLX. There was good correlation between CT scanogram and weight-bearing X-ray measurements in normally-aligned knees. However, as expected, in the malaligned lower limb, the influence of weight-bearing is critical which demonstrates the significance of weight-bearing X-rays


Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_3 | Pages 89 - 89
23 Feb 2023
Marasco S Gieroba T Di Bella C Babazadeh S Van Bavel D
Full Access

Identifying and restoring alignment is a primary aim of total knee arthroplasty (TKA). In the coronal plane, the pre-pathological hip knee angle can be predicted using an arithmetic method (aHKA) by measuring the medial proximal tibial angle (MPTA) and lateral distal femoral angle (aHKA=MPTA - LDFA). The aHKA is shown to be predictive of coronal alignment prior to the onset of osteoarthritis; a useful guide when considering a non-mechanically aligned TKA. The aim of this study is to investigate the intra- and inter-observer accuracy of aHKA measurements on long leg standing radiographs (LLR) and preoperative Mako CT planning scans (CTs).

Sixty-eight patients who underwent TKA from 2020–2021 with pre-operative LLR and CTs were included. Three observers (Surgeon, Fellow, Registrar) measured the LDFA and MPTA on LLR and CT independently on three separate occasions, to determine aHKA. Statistical analysis was undertaken with Bland-Altman test and coefficient of repeatability.

An average intra-observer measurement error of 3.5° on LLR and 1.73° on CTs for MPTA was detected. Inter-observer errors were 2.74° on LLR and 1.28° on CTs. For LDFA, average intra-observer measurement error was 2.93° on LLR and 2.3° on CTs, with inter-observer errors of 2.31° on LLR and 1.92° on CTs. Average aHKA intra-observer error was 4.8° on LLR and 2.82° on CTs. Inter-observer error of 3.56° for LLR and 2.0° on CTs was measured.

The aHKA is reproducible on both LLR and CT. CT measurements are more reproducible both between and within observers. The difference between measurements using LLR and CT is small and hence these two can be considered interchangeable. CT may obviate the need for LLRs and may overcome difficulties associated with positioning, rotation, body habitus and flexion contractures when assessing coronal alignment.


Background. There are limited previous findings detailed biomechanical properties following implantation with mechanical and kinematic alignment method in robotic total knee arthroplasty (TKA) during walking. The purpose of this study was to compare clinical and radiological outcomes between two groups and gait analysis of kinematic, and kinetic parameters during walking to identify difference between two alignment method in robotic total knee arthroplasty. Methods. Sixty patients were randomly assigned to undergo robotic-assisted TKA using either the mechanical (30 patients) or the kinematic (30 patients) alignment method. Clinical outcomes including varus and valgus laxities, ROM, HSS, KSS and WOMAC scores and radiological outcomes were evaluated. And ten age and gender matched patients of each group underwent gait analysis (Optic gait analysis system composed with 12 camera system and four force plate integrated) at minimum 5 years post-surgery. We evaluated parameters including knee varus moment and knee varus force, and find out the difference between two groups. Results. The mean follow up duration of both group was 8.1 years (mechanical method) and 8.0 years (kinematic method). Clinical outcome between two groups showed no significant difference in ROM, HSS, WOMAC, KSS pain score at last follow up. Varus and valgus laxity assessments showed no significant inter-group difference. We could not find any significant difference in mechanical alignment of the lower limb and perioperative complicatoin. In gait analysis, no significant spatiotemporal, kinematic or kinetic parameter differences including knee varus moment (mechanical=0.33, kinematic=0.16 P0.5) and knee varus force (mechanical=0.34, kinematic=0.37 P0.5) were observed between mechanical and kinematic groups. Conclusions. The results of this study show that mechanical and kinematic alignment method provide comparable clinical and radiological outcomes after robotic total knee arthroplasty in average 8 years follow-up. And no functional difference were found between two knee alignment methods during walking


Background. There are limited previous findings detailed biomechanical properties following implantation with mechanical and kinematic alignment method in robotic total knee arthroplasty (TKA) during walking. The purpose of this study was to compare clinical and radiological outcomes between two groups and gait analysis of kinematic, and kinetic parameters during walking to identify difference between two alignment method in robotic total knee arthroplasty. Methods. Sixty patients were randomly assigned to undergo robotic-assisted TKA using either the mechanical (30 patients) or the kinematic (30 patients) alignment method. Clinical outcomes including varus and valgus laxities, ROM, HSS, KSS and WOMAC scores and radiological outcomes were evaluated. And ten age and gender matched patients of each group underwent gait analysis (Optic gait analysis system composed with 12 camera system and four force plate integrated) at minimum 5 years post-surgery. We evaluated parameters including knee varus moment and knee varus force, and find out the difference between two groups. Results. The mean follow up duration of both groups was 8.1 years (mechanical method) and 8.0 years (kinematic method). Clinical outcome between two groups showed no significant difference in ROM, HSS, WOMAC, KSS pain score at last follow up. Varus and valgus laxity assessments showed no significant inter-group difference. We could not find any significant difference in mechanical alignment of the lower limb and perioperative complicatoin. In gait analysis, no significant spatiotemporal, kinematic or kinetic parameter differences including knee varus moment (mechanical=0.33, kinematic=0.16 P0.5) and knee varus force (mechanical=0.34, kinematic=0.37 P0.5) were observed between mechanical and kinematic groups. Conclusions. The results of this study show that mechanical and kinematic alignment method provide comparable clinical and radiological outcomes after robotic total knee arthroplasty in average 8 years follow-up. And no functional differences were found between two knee alignment methods during walking


Orthopaedic Proceedings
Vol. 103-B, Issue SUPP_1 | Pages 58 - 58
1 Feb 2021
Sires J Wilson C
Full Access

Robotic-assisted technology in total knee arthroplasty (TKA) aims to increase implantation accuracy, with real-time data being used to estimate intraoperative component alignment. Postoperatively, Perth computed tomography (CT) protocol is a valid measurement technique in determining both femoral and tibial component alignments. The aim of this study was to evaluate the accuracy of intraoperative component alignment by robotic-assisted TKA through CT validation. A total of 33 patients underwent TKA using the MAKO robotic-assisted TKA system. Intraoperative measurements of both femoral and tibial component placements, as well as limb alignment as determined by the MAKO software were recorded. Independent postoperative Perth CT protocol was obtained (n.29) and compared with intraoperative values. Mean absolute difference between intraoperative and postoperative measurements for the femoral component were 1.17 degrees (1.10) in the coronal plane, 1.79 degrees (1.12) in the sagittal plane, and 1.90 degrees (1.88) in the transverse plane. Mean absolute difference between intraoperative and postoperative measurements for the tibial component were 1.03 degrees (0.76) in the coronal plane and 1.78 degrees (1.20) in the sagittal plane. Mean absolute difference of limb alignment was 1.29 degrees (1.25), with 93.10% of measurements within 3 degrees of postoperative CT measurements. Overall, intraoperatively measured component alignment as estimated by the MAKO robotic-assisted TKA system is comparable to CT-based measurements.


Bone & Joint Open
Vol. 1, Issue 7 | Pages 339 - 345
3 Jul 2020
MacDessi SJ Griffiths-Jones W Harris IA Bellemans J Chen DB

Aims

An algorithm to determine the constitutional alignment of the lower limb once arthritic deformity has occurred would be of value when undertaking kinematically aligned total knee arthroplasty (TKA). The purpose of this study was to determine if the arithmetic hip-knee-ankle angle (aHKA) algorithm could estimate the constitutional alignment of the lower limb following development of significant arthritis.

Methods

A matched-pairs radiological study was undertaken comparing the aHKA of an osteoarthritic knee (aHKA-OA) with the mechanical HKA of the contralateral normal knee (mHKA-N). Patients with Grade 3 or 4 Kellgren-Lawrence tibiofemoral osteoarthritis in an arthritic knee undergoing TKA and Grade 0 or 1 osteoarthritis in the contralateral normal knee were included. The aHKA algorithm subtracts the lateral distal femoral angle (LDFA) from the medial proximal tibial angle (MPTA) measured on standing long leg radiographs. The primary outcome was the mean of the paired differences in the aHKA-OA and mHKA-N. Secondary outcomes included comparison of sex-based differences and capacity of the aHKA to determine the constitutional alignment based on degree of deformity.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXXVIII | Pages 47 - 47
1 Sep 2012
Wilson JA Dunbar MJ
Full Access

Purpose

To characterize the knee kinematic profiles of total knee arthroplasty patient knees intraoperatively, before implant insertion, using principal component analysis.

Method

Ninety-two patientsreceived Stryker Triathlon total knee arthroplasty (TKA) implants. The Stryker surgical navigation system was used for all surgeries. The system was used to define rigid bodies representing the femur and tibia, and to track the three-dimensional movement of the knee joint during surgery. Each knee was moved through a passive range of knee flexion/extension before and after implantation of the arthroplasty components. The frontal plane (medial-lateral) movement of the knee joint through a range of 10 to 120 degrees of flexion before implantation was calculated for each knee using the joint coordinate system (referred to as the pre-implant knee kinematic curve). Visual inspection of these patterns indicated three predominant curve types: a backward S shape, a backward C shape and a valgus to varus shape. Each curve was subjectively categorized into one of these three categories. Principal component analysis (PCA), a multivariate statistical analysis technique, was applied to the pre-implant knee kinematic pattern data to objectively extract the major patterns of curve types within the 92 knees. Analysis of variance was used to compare the mean differences in PC scores between the curve shape groups to confirm visual categorization.


Orthopaedic Proceedings
Vol. 88-B, Issue SUPP_III | Pages 428 - 428
1 Oct 2006
Zaccherotti G Mondanelli M Rosati E Moraldi G
Full Access

Purpose of this experimental-prospective study on 35 total knee prostheses is to compare the data related to the bone cuts imposed during surgery using PIGalileo navigator and those really gotten and measured by TC scan examination at follow-up. PIGalileo navigator consists of a photogrammetric infrared camera that links a computer to three reflecting sensories fixed on femur and tibia. At follow-up, all the knees were submitted to a spiral TC analysis making a sequential 3 mm axial scans. In six cases (17%) it has not been possible complete the operation utilizing the navigator. Any statistically significance has been found regarding the mechanical axes of the femur and the tibia, the sagittal rotation of the femur and the horizontal rotation of the tibia. High level of statistical significance has been noted for the horizontal rotation of the femur (intraop: 3.7° extra vs. TC: 0.2° intra; p=.006) and for the sagittal rotation of the tibia (intraop: 6.2° post vs. TC: 3.5° post; p = .003). PIGalileo navigator has shown effectiveness to reproduce bone cuts respect the major axes of the knee but it has been less precise in rotation, mainly for the femoral cut.


Bone & Joint Open
Vol. 3, Issue 10 | Pages 767 - 776
5 Oct 2022
Jang SJ Kunze KN Brilliant ZR Henson M Mayman DJ Jerabek SA Vigdorchik JM Sculco PK

Aims. Accurate identification of the ankle joint centre is critical for estimating tibial coronal alignment in total knee arthroplasty (TKA). The purpose of the current study was to leverage artificial intelligence (AI) to determine the accuracy and effect of using different radiological anatomical landmarks to quantify mechanical alignment in relation to a traditionally defined radiological ankle centre. Methods. Patients with full-limb radiographs from the Osteoarthritis Initiative were included. A sub-cohort of 250 radiographs were annotated for landmarks relevant to knee alignment and used to train a deep learning (U-Net) workflow for angle calculation on the entire database. The radiological ankle centre was defined as the midpoint of the superior talus edge/tibial plafond. Knee alignment (hip-knee-ankle angle) was compared against 1) midpoint of the most prominent malleoli points, 2) midpoint of the soft-tissue overlying malleoli, and 3) midpoint of the soft-tissue sulcus above the malleoli. Results. A total of 932 bilateral full-limb radiographs (1,864 knees) were measured at a rate of 20.63 seconds/image. The knee alignment using the radiological ankle centre was accurate against ground truth radiologist measurements (inter-class correlation coefficient (ICC) = 0.99 (0.98 to 0.99)). Compared to the radiological ankle centre, the mean midpoint of the malleoli was 2.3 mm (SD 1.3) lateral and 5.2 mm (SD 2.4) distal, shifting alignment by 0.34. o. (SD 2.4. o. ) valgus, whereas the midpoint of the soft-tissue sulcus was 4.69 mm (SD 3.55) lateral and 32.4 mm (SD 12.4) proximal, shifting alignment by 0.65. o. (SD 0.55. o. ) valgus. On the intermalleolar line, measuring a point at 46% (SD 2%) of the intermalleolar width from the medial malleoli (2.38 mm medial adjustment from midpoint) resulted in knee alignment identical to using the radiological ankle centre. Conclusion. The current study leveraged AI to create a consistent and objective model that can estimate patient-specific adjustments necessary for optimal landmark usage in extramedullary and computer-guided navigation for tibial coronal alignment to match radiological planning. Cite this article: Bone Jt Open 2022;3(10):767–776


Bone & Joint Research
Vol. 13, Issue 5 | Pages 226 - 236
9 May 2024
Jürgens-Lahnstein JH Petersen ET Rytter S Madsen F Søballe K Stilling M

Aims. Micromotion of the polyethylene (PE) inlay may contribute to backside PE wear in addition to articulate wear of total knee arthroplasty (TKA). Using radiostereometric analysis (RSA) with tantalum beads in the PE inlay, we evaluated PE micromotion and its relationship to PE wear. Methods. A total of 23 patients with a mean age of 83 years (77 to 91), were available from a RSA study on cemented TKA with Maxim tibial components (Zimmer Biomet). PE inlay migration, PE wear, tibial component migration, and the anatomical knee axis were evaluated on weightbearing stereoradiographs. PE inlay wear was measured as the deepest penetration of the femoral component into the PE inlay. Results. At mean six years’ follow-up, the PE wear rate was 0.08 mm/year (95% confidence interval 0.06 to 0.09 mm/year). PE inlay external rotation was below the precision limit and did not influence PE wear. Varus knee alignment did not influence PE wear (p = 0.874), but increased tibial component total translation (p = 0.041). Conclusion. The PE inlay was well fixed and there was no relationship between PE stability and PE wear. The PE wear rate was low and similar in the medial and lateral compartments. Varus knee alignment did not influence PE wear. Cite this article: Bone Joint Res 2024;13(5):226–236


Bone & Joint Open
Vol. 4, Issue 4 | Pages 262 - 272
11 Apr 2023
Batailler C Naaim A Daxhelet J Lustig S Ollivier M Parratte S

Aims. The impact of a diaphyseal femoral deformity on knee alignment varies according to its severity and localization. The aims of this study were to determine a method of assessing the impact of diaphyseal femoral deformities on knee alignment for the varus knee, and to evaluate the reliability and the reproducibility of this method in a large cohort of osteoarthritic patients. Methods. All patients who underwent a knee arthroplasty from 2019 to 2021 were included. Exclusion criteria were genu valgus, flexion contracture (> 5°), previous femoral osteotomy or fracture, total hip arthroplasty, and femoral rotational disorder. A total of 205 patients met the inclusion criteria. The mean age was 62.2 years (SD 8.4). The mean BMI was 33.1 kg/m. 2. (SD 5.5). The radiological measurements were performed twice by two independent reviewers, and included hip knee ankle (HKA) angle, mechanical medial distal femoral angle (mMDFA), anatomical medial distal femoral angle (aMDFA), femoral neck shaft angle (NSA), femoral bowing angle (FBow), the distance between the knee centre and the top of the FBow (DK), and the angle representing the FBow impact on the knee (C’KS angle). Results. The FBow impact on the mMDFA can be measured by the C’KS angle. The C’KS angle took the localization (length DK) and the importance (FBow angle) of the FBow into consideration. The mean FBow angle was 4.4° (SD 2.4; 0 to 12.5). The mean C’KS angle was 1.8° (SD 1.1; 0 to 5.8). Overall, 84 knees (41%) had a severe FBow (> 5°). The radiological measurements showed very good to excellent intraobserver and interobserver agreements. The C’KS increased significantly when the length DK decreased and the FBow angle increased (p < 0.001). Conclusion. The impact of the diaphyseal femoral deformity on the mechanical femoral axis is measured by the C’KS angle, a reliable and reproducible measurement. Cite this article: Bone Jt Open 2023;4(4):262–272


Orthopaedic Proceedings
Vol. 104-B, Issue SUPP_7 | Pages 87 - 87
1 Jul 2022
Rajput V Fontalis A Plastow R Kayani B Giebaly D Hansejee S Magan A Haddad F
Full Access

Abstract. Introduction. Coronal plane alignment of the knee (CPAK) classification utilises the native arithmetic hip-knee alignment to calculate the constitutional limb alignment and joint line obliquity which is important in pre-operative planning. The objective of this study was to compare the accuracy and reproducibility of measuring the lower limb constitutional alignment with the traditional long leg radiographs versus computed tomography (CT) used for pre-operative planning in robotic-arm assisted TKA. Methods. Digital long leg radiographs and pre-operative CT scan plans of 42 patients (46 knees) with osteoarthritis undergoing robotic-arm assisted total knee replacement were analysed. The constitutional alignment was established by measuring the medial proximal tibial angle (mPTA), lateral distal femoral angle (LDFA), weight bearing hip knee alignment (WBHKA), arithmetic hip knee alignment (aHKA) and joint line obliquity (JLO). Furthermore, the Coronal Plane Alignment of the Knee (CPAK) classification was utilised to classify the patients based on their coronal knee alignment phenotype. Results. Mean age of the patients was 66 years (SD 9) and mean BMI 31.2 (SD 3.9). There were 27 left and 19 right sided surgeries. The Pearson's corelation coefficient was 0.722 (p=0.008) for WBHKA; 0.729 (p<0.001) for MPTA; 0.618 (p=0.14) for aHKA; 0.502 (p= 0.04) for LDFA and 0.305 (p=0.234) for JLO. CPAK classification was concordant for 53% study participants between the two groups. Conclusion. Three-dimensional CT-based modelling with computer software more accurately predicts constitutional limb alignment and JLO as defined by the CPAK classification compared to plain long-leg radiographs in pre-operative planning of total knee arthroplasty


Bone & Joint 360
Vol. 12, Issue 4 | Pages 16 - 20
1 Aug 2023

The August 2023 Knee Roundup. 360. looks at: Curettage and cementation of giant cell tumour of bone: is arthritis a given?; Anterior knee pain following total knee arthroplasty: does the patellar cement-bone interface affect postoperative anterior knee pain?; Nickel allergy and total knee arthroplasty; The use of artificial intelligence for the prediction of periprosthetic joint infection following aseptic revision total knee arthroplasty; Ambulatory unicompartmental knee arthroplasty: development of a patient selection tool using machine learning; Femoral asymmetry: a missing piece in knee alignment; Needle arthroscopy – a benefit to patients in the outpatient setting; Can lateral unicompartmental knees be done in a day-case setting?


Bone & Joint Open
Vol. 5, Issue 2 | Pages 101 - 108
6 Feb 2024
Jang SJ Kunze KN Casey JC Steele JR Mayman DJ Jerabek SA Sculco PK Vigdorchik JM

Aims. Distal femoral resection in conventional total knee arthroplasty (TKA) utilizes an intramedullary guide to determine coronal alignment, commonly planned for 5° of valgus. However, a standard 5° resection angle may contribute to malalignment in patients with variability in the femoral anatomical and mechanical axis angle. The purpose of the study was to leverage deep learning (DL) to measure the femoral mechanical-anatomical axis angle (FMAA) in a heterogeneous cohort. Methods. Patients with full-limb radiographs from the Osteoarthritis Initiative were included. A DL workflow was created to measure the FMAA and validated against human measurements. To reflect potential intramedullary guide placement during manual TKA, two different FMAAs were calculated either using a line approximating the entire diaphyseal shaft, and a line connecting the apex of the femoral intercondylar sulcus to the centre of the diaphysis. The proportion of FMAAs outside a range of 5.0° (SD 2.0°) was calculated for both definitions, and FMAA was compared using univariate analyses across sex, BMI, knee alignment, and femur length. Results. The algorithm measured 1,078 radiographs at a rate of 12.6 s/image (2,156 unique measurements in 3.8 hours). There was no significant difference or bias between reader and algorithm measurements for the FMAA (p = 0.130 to 0.563). The FMAA was 6.3° (SD 1.0°; 25% outside range of 5.0° (SD 2.0°)) using definition one and 4.6° (SD 1.3°; 13% outside range of 5.0° (SD 2.0°)) using definition two. Differences between males and females were observed using definition two (males more valgus; p < 0.001). Conclusion. We developed a rapid and accurate DL tool to quantify the FMAA. Considerable variation with different measurement approaches for the FMAA supports that patient-specific anatomy and surgeon-dependent technique must be accounted for when correcting for the FMAA using an intramedullary guide. The angle between the mechanical and anatomical axes of the femur fell outside the range of 5.0° (SD 2.0°) for nearly a quarter of patients. Cite this article: Bone Jt Open 2024;5(2):101–108