No effect of obesity on limb and component alignment after computer-assisted total knee arthroplasty

doi:10.1016/j.knee.2014.04.004

The Knee

Volume 21, Issue 4, August 2014, Pages 862-865

https://doi.org/10.1016/j.knee.2014.04.004 Get rights and content

Highlights

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Limb and component alignment accuracy was checked after navigated TKA in the obese
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Limb and component alignment were measured on hip-to-ankle radiographs
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These were compared between obese and non-obese groups
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No significant difference in postoperative alignment was found between the groups
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Navigation will help achieve consistently accurate alignment in the obese

Abstract

Purpose

This retrospective study aimed to determine if computer navigation provides consistent accuracy for limb and component alignment during TKA irrespective of body mass index (BMI) by comparing limb and component alignment and the outlier rates in obese versus non-obese individuals undergoing computer-assisted TKA.

Methods

Six hundred and thirty-five computer assisted total knee arthroplasties (TKAs) performed in non-obese individuals (BMI < 30 kg/m²) were compared with 520 computer-assisted TKAs in obese individuals (BMI ≥ 30 kg/m²) for postoperative limb and component alignment using full length standing hip-to-ankle radiographs.

Results

No significant difference in postoperative limb alignment (179.7° ± 1.7° vs 179.6° ± 1.8°), coronal femoral (90.2° ± 1.6° vs 89.8° ± 1.9°) and tibial component (90.2° ± 1.6° vs 90.3° ± 1.7°) alignment and outlier rates (6.2% vs 7.5%) was found between non-obese and obese individuals. Similarly, alignment and the outlier rates were similar when non-obese individuals and a subgroup of morbidly obese individuals (BMI > 40 kg/m²) were compared.

Conclusions

Computer navigation can achieve excellent limb and component alignment irrespective of a patient's BMI. Although obesity may not be an indication per se for using computer navigation during TKA, it will help achieve consistently accurate limb and component alignment in obese patients.

Level of Evidence

Level II

Introduction

Risk of revision after total knee arthroplasty (TKA) is significantly higher when obesity is combined with malalignment of tibial component or the limb [1]. Reports have suggested that implant survival is significantly lower in obese patients (60–92%) in the long-term when compared to non-obese individuals (89–98.5%) [2], [3], [4], [5], [6] with loosening of tibial components and polyethylene wear being the major causes of revision [4], [5]. Hence it is all the more important to ensure symmetric loading of implant and bone in the obese by accurate implant positioning and restoration of mechanical axis.

Conventional techniques have shown lower consistency in achieving accurate limb and component alignment when compared to navigation techniques during TKA [7], [8], [9], [10], [11], [12], [13], [14]. Furthermore, recent studies have reported greater risk for limb malalignment with conventional TKAs when performed in the obese [15], [16]. Computer navigation using the optical tracking system locates the centre of the femoral head, centre of the knee joint and the centre of the ankle to calculate the mechanical axis of the limb. However, during navigated TKA, obese patients may be prone to errors due to difficulty in exposing, palpating and registering important bony landmarks such as the malleoli and the femoral epicondyles. Although several studies have validated the accuracy and consistency of computer-assisted navigation and have reported significant improvement in component orientation and limb alignment in TKA with computer navigation [7], [8], [9], [10], [11], [12], [13], [14], literature is lacking for limb and component alignment in computer-assisted TKA in the obese.

Accuracy of computer navigation during TKA in the obese has not been studied and whether computer navigation achieves the same degree of accurate limb and component alignment in the obese individuals vis-a-vis non-obese patients is not known. Hence, the purpose of the present study was to determine if computer navigation provides consistent accuracy for limb and component alignment during TKA irrespective of body mass index (BMI) by comparing limb and component alignment and the outlier rates in obese versus non-obese individuals undergoing computer-assisted TKA. Our hypothesis was that limb and component alignment will not be significantly different when obese and non-obese individuals were compared after computer-assisted TKA.

Section snippets

Patients and methods

We retrospectively reviewed the clinical and radiographic records of 1500 computer-assisted TKAs (in 1250 patients) performed between 2005 and 2009. Non-obese individuals were defined as those having a BMI of < 30 kg/m² (calculated by dividing the subject's weight in kilogrammes by their height in metres squared), obese individuals were defined as those having a BMI of ≥ 30 kg/m² and morbidly obese individuals were defined as those having BMI > 40 kg/m². The inclusion criteria were primary

Results

Demographic and radiographic parameters in the non-obese, obese and morbidly obese groups are summarised in Table 1. Postoperatively, the limb alignment (mean HKA angle) was not significantly different when the non-obese group was compared with the obese group (p = 0.33) and when the non-obese group was compared with the morbidly obese group (p = 0.20). Although the postoperative coronal alignment of the femoral component was not significantly different when the non-obese group was compared to the

Discussion

Despite showing superior and consistent results in the restoration of limb and component alignment, the technical challenges during computer-assisted TKA in obese individuals remain. Obese patients may be prone to errors due to difficulty in registering the femoral head centre because of substantial weight of the leg and difficulty in registering the ankle centre due to difficulty in palpating the malleoli. Furthermore, excessive fat makes effective exposure difficult in the obese and excessive

Conflict of interest statement

The authors wish to state that no funds or benefits were received by any of the authors in support of this study/article from any source.

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There are more references available in the full text version of this article.

Cited by (18)

Robotic-Assisted Total Knee Arthroplasty in Obese Patients
2024, Arthroplasty Today
Robotic-assisted systems have gained popularity in total knee arthroplasty (TKA). The purpose of this study was to evaluate operative characteristics and radiographic outcomes of obese patients undergoing robotic-assisted TKA.
A retrospective review of consecutive cases performed by a single surgeon was performed from January 1, 2016, to January 31, 2022. Adult patients with body mass index ≥35 kg/m² who underwent primary TKA using a computed tomography–assisted robotic system were compared to patients who underwent primary TKA using conventional instrumentation. Demographics, preoperative and postoperative radiographic measurements, and intraoperative outcomes were compared between cohorts. In total, 119 patients were identified, 60 in the robotic-assisted cohort and 59 in the conventional instrumentation cohort.
Age, body mass index, and estimated blood loss were not significantly different between the cohorts. The robotic-assisted cohort experienced longer tourniquet times (93.3 vs 75.5 minutes, P < .001). Preoperative hip-knee-ankle angle (HKA) was similar between the robotic-assisted and conventional cohorts (8.4° ± 4.9° vs 9.3° ± 5.3°, P = .335). Postoperative HKA was 2.0° ± 1.4° in the robotic-assisted group and 3.1° ± 3.23° in the conventional group (P = .040). The proportion of patients with postoperative HKA > 3° of varus or valgus was 9 of 60 (15.0%) in the robotic-assisted cohort compared to 18 of 59 (30.5%) using conventional instrumentation (P = .043).
Obese patients treated with robotic-assisted TKA had postoperative alignment closer to neutral and fewer postoperative radiographic outliers than patients treated with conventional instrumentation. The results of this study support use of robotic-assisted technologies in TKA, particularly in obese patients.
Navigated total knee arthroplasty: Retrospective study of 600 continuous cases
2021, Revue de Chirurgie Orthopedique et Traumatologique
La chirurgie de genou naviguée existe depuis plus d’une vingtaine d’année mais son utilisation reste marginale. Son intérêt reste en effet largement débattu notamment en ce qui concerne son efficacité dans l’obtention de l’alignement postopératoire souhaité.
L’hypothèse de cette étude était qu’un HKA neutre (180 ± 3) serait obtenu dans au moins 85 % des cas et qu’il n’existerait pas de différence entre les stations de navigation utilisées.
Dans cette étude rétrospective monocentrique, mono-opérateur, toutes les PTG réalisées de septembre 2003 à décembre 2017 ont été incluses, soit un total de 753 PTG naviguées : 196 prothèses Natural Knee II (Zimmer) avec le système Navitrack-OS Knee (Zimmer CAS) groupe Navitrack et 557 prothèses (196 Profix, Smith et Nephew et 361 LCS, Depuy) avec le système Brainlab Vector Vision, groupe Brainlab. L’objectif de navigation indépendant de l’alignement préopératoire était toujours l’obtention d’un axe mécanique HKA neutre (180 ± 3). Le critère d’évaluation principal était l’HKA postopératoire. Cette mesure a permis de déterminer si l’objectif de navigation était atteint, de définir le pourcentage de patient hors cible et de comparer les systèmes de navigation entre eux. L’influence éventuelle des facteurs sexe, indice de masse corporelle (IMC) et déformation préopératoire a été secondairement étudiée. Enfin, les valeurs finales de navigation ont été comparées aux données radiologiques afin de déceler d’éventuelles déviations.
Au total, 600 cas ont pu être exploités, 160 dans le groupe Navitrack et 440 dans le groupe Brainlab (152 Profix et 288 LCS). Un HKA neutre était retrouvé chez 90,8 % des patients : 93,1 % pour le groupe Navitrack et 90 % dans le groupe Brainlab (90,8 % Profix et 89,6 % LCS). Il n’existait pas de différence significative entre les groupes (p = 0,68), ni après analyse en sous-groupes (p = 0,85). Un IMC élevé est un facteur influençant négativement l’obtention d’un HKA neutre (p = 0,015), et ce, quel que soit le système utilisé.
Dans notre étude, portant sur 600 PTG naviguées, l’objectif d’alignement postopératoire (HKA 180 ± 3) était atteint dans 91 % des cas. Aucune différence n’était retrouvée entre les navigateurs. Les patients avec un IMC élevé étaient plus à risque d’être hors cible (p = 0,015).
IV.
Navigated total knee arthroplasty: Retrospective study of 600 continuous cases
2021, Orthopaedics and Traumatology: Surgery and Research
Citation Excerpt :
In our study, sex, age and preoperative alignment had no impact on the results. Shetty et al. [21] found no difference in the implantation accuracy in obese versus normal-BMI patients with navigation. Conversely, Gaillard et al. [22] found that the positioning of the tibial component was less accurate in obese patients.
Computer-assisted navigation in total knee arthroplasty (TKA) has existed for more than 20 years, although its use has been marginal. Its benefits are still largely debated, especially its efficacy for achieving the desired postoperative alignment.
A neutral hip-knee-ankle (HKA) angle (180° ± 3°) will be achieved in at least 85% of cases and there will be no difference between the different types of navigation systems used.
In this retrospective, single-center, single-surgeon study, all the TKAs completed between September 2003 and December 2017 were included, giving a total of 753 navigated TKAs: Navitrack group: 196 Natural Knee II implants (Zimmer) with the Navitrack-OS Knee system (Zimmer CAS); Brainlab group: 557 implants (196 Profix, Smith & Nephew and 361 LCS, DePuy) with the Brainlab Vector Vision system. The aim of navigation was independent of the preoperative alignment and was always to achieve a neutral HKA mechanical axis (180° ± 3°). The primary endpoint was the postoperative HKA angle. This parameter was used to determine whether the navigation objective was achieved, to define how many patients were outliers and to compare navigation systems to each other. The potential influence of sex, body mass index (BMI) and preoperative deformity were secondary aims. Lastly, the final navigation values were compared to radiological data to detect any potential deviations.
We analyzed 600 of the cases, 160 in the Navitrack group and 440 in the Brainlab group (152 Profix and 288 LCS). A neutral HKA angle was found in 91% patients: 93% for the Navitrack group and 90% in the Brainlab group (90.8% Profix and 89.6% LCS). There was no significant difference between groups (p = 0.68), nor between subgroups (p = 0.85). An elevated BMI negatively influenced the ability to achieve a neutral HKA (p = 0.015), regardless of the system used.
In our study of 600 TKA cases done with navigation, the postoperative alignment goal (HKA 180° ± 3°) was achieved in 91% of cases. There was no difference between navigation systems. Patients with a high BMI were more likely to be outliers (p = 0.015).
IV.
No influence of obesity on mid-term clinical, functional, and radiological results after computer-navigated total knee arthroplasty using a gap balancing technique
2021, Journal of Clinical Orthopaedics and Trauma
Citation Excerpt :
This can affect the size and position of the femur component which can influence the outcome. Therefore, with the rising number of obese patients, and paucity of literature on the influence of obesity on radiological2,27,28 and functional2,27 outcome after navigated TKA, the present study was done to a) determine if computer navigation provides consistent accuracy for limb and component alignment in obese sub-group of patients like in non-obese patients and b) to know if navigation achieves similar clinical and functional results in obese and non-obese patients when GB technique is used, at the end of 5 years after TKA. We prospectively studied the clinical, functional, and radiographic results of 187 consecutive computer-assisted TKAs performed between 2012 January and 2015 January, in 136 patients.
In obese patients, thick subcutaneous tissue can introduce errors during registration and leg weight can influence gap balancing in navigated TKA. Present study is done to determine if computer navigated TKA using a gap balancing technique can achieve consistent accuracy for limb and component alignment, and similar clinical and functional results in obese patients like in non-obese patients.
We prospectively compared the radiological, clinical, and functional results of 78 knees in 57 non-obese patients and 79 knees in 58 obese patients who underwent computer-assisted TKA. Non-obese individuals were defined as those having BMI of <30 kg/m² and obese individuals as BMI ≥30 kg/m². The degree of knee deformity was calculated by Hip – Knee – Ankle (HKA) angle and clinical and functional assessment was done using the Knee Society Score – clinical knee score and Knee Society Score - function score, respectively. All these were documented before and at 6 months, 2 year, and 5 years after TKA.
The outlier rate of postoperative limb alignment (HKA angle) was 8.9% in the obese group which was not significantly different (p =1.00) from that of the non-obese group (7.7%). Mean clinical knee scores were not significantly different between the non-obese and obese groups preoperatively (58.8 vs 57.4, p = 0.14) and at 6 months (92.7 vs 91, p = 0.06), 2 years (91.4 vs 90, p = 0.07), and 5 years (92.4 vs 91.3, p = 0.1) post-surgery. Similarly, mean functional scores were not significantly different between the non-obese and obese groups preoperatively (50.9 vs 49.9, p = 0.31) and at 6 months (92.7 vs 90.9, p = 0.06), 2 years (91.3 vs 92, p = 0.44), and 5 years (90.6 vs 91.1, p = 0.51) post-surgery.
Obesity has no influence on mid-term clinical, functional, and radiological results after computer navigated TKA, done by gap balancing technique.
Therapeutic level II.
Four-Millimeter Additional Bone Resection in the Distal Femur Does Not Result in an Equivalent Increase in the Extension Joint Gap in Total Knee Arthroplasty
2021, Journal of Arthroplasty
Additional bone resection in the distal femur is performed to increase the extension joint gap in total knee arthroplasty (TKA). The present study aimed to analyze the relationship between the amount of additional bone resection in the distal femur and the increase in the extension joint gap in TKA.
Fifty knees undergoing TKA for varus osteoarthritis were evaluated. Two femoral trial component models were prepared: (1) a normal model with 9-mm-thick distal and posterior femoral components and (2) an additional bone resection model with a 5-mm-thick distal femoral component (9 mm to 4 mm) and a 9-mm-thick posterior femoral component, which simulated an additional bone cut in the distal femur of 4 mm. The femoral trial component models were set before implantation, and the extension joint gap was measured using a tensor device that had a shape identical to that of the fixed-bearing tibial insert.
The additional bone resection model had a larger joint gap than the normal model (P < .01). The mean extension gap increase in the additional bone resection model was 2 (standard deviation 1) mm, which was less than the thickness of the additional bone resection (4 mm) (P < .01).
The amount of additional bone resection in the distal femur was not equal to the increase in the extension joint gap. Additional bone resection of 4 mm in the distal femur only increased the extension joint gap by a mean of 2 mm.
Clinical and radiographic outcomes of computer-navigated total knee arthroplasty are not adversely affected by body mass index
2020, Journal of Orthopaedics
Citation Excerpt :
This further complicates the surgical management of such patients. However through the use of computer navigation, Shetty et al. reported that there was no significant difference in post-operative lower limb alignment between the obese and non-obese.8 Likewise, Yogeesh et al. reported that there was no significant difference in operating time with computer navigated knee arthroplasty between the obese and non-obese.9
To study the effect of obesity on clinical and radiographic outcomes of computer-navigated knee arthroplasty.
117 patients underwent primary computer-navigated total knee arthroplasty. Eight were lost to follow-up and 8 had incomplete data.
Eighty-four (83.2%) female, 17 (16.8%) male patients age 65.3 ± 6.9 years with a pre-operative BMI 27.2 ± 4.1 (18.6–40.0) kg/m², 7.3 ± 0.98 years follow-up. Forty-two (41.6%) had a BMI>27.5 kg/m² indicative of obesity in Singapore. Post-operative radiographic alignment, 2-year Oxford knee scores and ROM were not significantly associated with BMI.
BMI is not a determinant of functional scores when computer navigation is used.

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^☆: No benefits or funds were received in support of this study by any of the authors. This article is original and has not been published before or currently submitted to any other journal.

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No effect of obesity on limb and component alignment after computer-assisted total knee arthroplasty☆

Highlights

Abstract

Purpose

Methods

Results

Conclusions

Level of Evidence

Introduction

Section snippets

Patients and methods

Results

Discussion

Conflict of interest statement

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