Total knee arthroplasty using a computerized assisted stereotaxic navigation system with bluetooth communication in obese patients - A randomized controlled study
Total knee arthroplasty using a computerized assisted stereotaxic navigation system with...
Rivkin, Gurion; Kandel, Leonid; Perets, Itay; Tsohar, Tamir; Nasrawy, Tarek; Liebergall, Meir
2023-12-31 00:00:00
COMPUTER ASSISTED SURGERY 2023, VOL. 28, NO. 1, 2162970 https://doi.org/10.1080/24699322.2022.2162970 RESEARCH ARTICLE Total knee arthroplasty using a computerized assisted stereotaxic navigation system with bluetooth communication in obese patients - A randomized controlled study a a a b a a Gurion Rivkin , Leonid Kandel , Itay Perets , Tamir Tsohar , Tarek Nasrawy and Meir Liebergall a b Department of Orthopedics, Hadassah Hebrew University Hospital, Jerusalem, Israel; Department of Physiotherapy and Rehabilitation, Hadassah Hebrew University Hospital, Jerusalem, Israel KEYWORDS ABSTRACT Total knee arthroplasty; Correct mechanical alignment (180 hip-knee-angle (HKA)) may be difficult to obtain on a con- obese; coronal alignment; sistent basis in obese patients. This is a randomized controlled study comparing the post-opera- navigation; prospective tive coronal alignment in obese patients between two surgical total knee arthroplasty (TKA) randomized trial techniques – conventional and computer assisted navigation. The primary outcome was the post-operative HKA. A total of 60 patients were assigned to undergo conventional total knee arthroplasty (30 patients) or computerized assisted stereotaxic navigation system with Bluetooth communication surgery (30 patients). One patient from the study group was excluded due to malfunction of the navigation system. Good quality x-rays were available in 57 patients. There was no difference between the groups. Post-operative HKA was 2.8 and 2.9 in the study and control groups, respectively (p¼ 0.87). In obese patients undergoing TKA, computerized naviga- tion had no impact on post-op HKA. Clincal Trial Registration Number: HMO 0092-13 Introduction The use of navigation systems in TKA have been shown to improve alignment and significantly reduce Obesity was declared a global epidemic in 2000 by outliers [8]. Thus, in this randomized controlled study, the World Health Organization, affecting both devel- the main aim was to compare the coronal radiological oped and developing countries regardless of socioeco- outcome of implant placement in obese patients (BMI nomic levels [1]. It is estimated that in the year 2030 > 30) using computerized assisted stereotaxic naviga- at least 40% of the US population will be obese (BMI tion system with Bluetooth communication versus >30), and greater than 10% will be severely obese conventional instrumentation in total knee arthro- (BMI > 40) [2]. The combination of aging population plasty. We hypothesized that the use of CAS would with obesity epidemic will lead to an increased inci- achieve better coronal alignment in obese patients. dence of knee osteoarthritis in obese patients. Although post-operative results of knee arthroplasty Material and methods may be similar for patients with high BMI [3], they are at increased risk of complications such as wound com- After obtaining approval from the ethical committee, plications, infection and medial collateral injury [4]. we performed a randomized, controlled trial that com- Long-term survival of TKA may be related to correct pared CAS to conventional instrumentation in patients prosthesis and knee alignment [5]. Correct alignment who underwent primary TKA. Sixty patients were may be more difficult to achieve in obese patients, enrolled; the study group consisted of 30 patients that where some of the anatomic landmarks are obscured underwent TKA with a computerized assisted stereo- by fatty soft tissue. Several studies showed the rela- taxic navigation system with Bluetooth communication tion between increased BMI and malalignment causing - the iAssistV Knee System (Zimmer Biomet CAS, increased risk of failure [5–7]. Montreal, Canada), and 30 control patients that CONTACT Gurion Rivkin gurion@hadassah.org.il Department of Orthopedics, Hadassah Hebrew University Hospital, Jerusalem, Israel 2023 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 2 G. RIVKIN ET AL. underwent TKA with conventional instrumentation. In Surgical technique V R both groups the Persona (Zimmer Biomet, Warsaw, All surgeries were performed by one of four surgeons IN) knee prosthesis was used. well versed in the navigation system. (GR, YM, LK Inclusion criteria were patients that underwent pri- and ML). mary TKA for the treatment of non-inflammatory Regional anesthesia was used in 50 patients and degenerative joint disease, over 18 years old, and BMI general anesthesia in 10 patients (Table 1). 30. Exclusion Criteria were active infection, severe In all arthroplasties, a medial parapatellar approach hip arthrosis, neurological and vascular disorders, pre- was used under tourniquet without patella eversion. vious ipsilateral knee surgery, hip or knee ankyloses, Patellae were not resurfaced. A posterior cruciate sacri- collateral ligament insufficiency and cancer. ficing knee implant was used in all cases. The study workflow is depicted in the attached The surgical technique of the study group consisted CONSORT flow chart (Figure 1). of navigated distal femoral and proximal tibia cuts. In Patients who had appropriate indication to the femoral side, the point of entry to the medullary be candidates for TKA and who met the specified inclusion and exclusion criteria, were informed Table 1. Study demographics. about the CAS and offered entry into the study. Study group Control p Value Informed consent was obtained from all patients Age 66.9 70.1 p¼ 0.014 Gender (female : male) 21:9 19:11 p¼ 0.58 and randomization then occurred. The randomization BMI 35.6 34.4 p¼ 0.265 process is discussed further under the randomiza- Anesthesia (regional : general) 25 : 5 25:5 p> 0.999 Surgery time 77 70 p¼ 0.098 tion procedure. Figure 1. The study workflow chart. COMPUTER ASSISTED SURGERY 3 canal was identified and a short rod was attached to it notch of the femur or femoral component). The tibial without piercing the medullary canal. A position sen- mechanical axis is defined by the center of the ankle sor (pod) was attached to the rod and a conical shape and the middle of the tibia plateau. movement of the thigh allowed the navigated system The study endpoints consisted of several different to identify the physiological femoral center of rotation. angles which were monitored to evaluate the lower A second pod was then attached to a cutting guide limb alignment. They are as follows: assembly and a perpendicular plane to the coronal mechanical axis was identified. The aim was for a dis- Primary outcomes The hip-knee-ankle (HKA) angle – the angle between tal femoral cut perpendicular to the mechanical axis the femoral and tibial mechanical axis. The primary cri- with 3 degrees of flexion in the sagittal plane. The rest of the femoral preparation was completed with a terion is that HKA should be in the range 180 ±3 , 4-in-1 technique setting external rotation at 3 degrees which is considered a correct position of the prosthesis. compared to the posterior condylar axis. For the tibial proximal cut an extramedullary type construct with a Secondary outcomes pod connected to it was attached to the malleoli and For easier calculations we used mechanical medial the tibial surface over the PCL attachment point. femoral distal angle (mMDFA), as described by Medial and lateral movement of the knee was used to Hirschmann et al. [9] the medial angle formed set the tibial mechanical alignment. A cutting guide between the mechanical femoral axis and the axis apparatus was attached to the proximal tibia medial to the tibial tubercle with a second pod connected. connecting most distal points of the medial and lateral femoral condyles. After the mechanical alignment was obtained the first Mechanical medial proximal tibial angle (mMPTA) – pod was also attached to the cutting guide assembly with an aim of a cut perpendicular to the coronal the medial angle formed between the mechanical tib- mechanical axis with a 3 degrees posterior slope in ial axis and the tibial tangent in the native knee. In the operated knee the tibial proximal angle is formed the sagittal plane. Conventional surgical technique consisted of an by the mechanical axis and the axis of the lower bor- intramedullary femoral alignment jig set at 5 degrees der of the tibial tray. valgus cut and extramedullary tibial alignment aimed at 90 degrees coronal plane cut and a 3 degrees pos- Randomization procedure terior slope in the sagittal plane. A random number series was generated and assigned The tourniquet was deflated after skin closure. with a unique number. Envelopes labeled with the All patients were treated with low molecular weight patient’s randomization number contained a sticker heparin (LMWH) 40 mg daily from post-operative day inside identifying the randomization group. The sur- (POD) 1. Full weight bearing was encouraged with a plan for home discharge. geon was provided with the envelopes and instruc- tions for using them before the start of the study. Prior to surgery, the envelope that contained the Radiographic measurements patient’s randomization number and treatment assign- Full-length standing anteroposterior radiographs were ment to one of the two groups – either the study group collected from all patients pre-operatively and at or the control group. The randomization envelopes were 6-weeks post-operatively. All x-rays collected were per- used in sequential order of patient enrollment. st th formed with the same technique of bipodal standing Between June 1 2015 and January 25 2017 a with no hip rotation and patella facing forward. The total of 508 TKAs were performed. Of these, 253 had a change in alignment of the knee and the position of BMI > 30. Sixty-four patients were excluded and 129 the tibial and femoral components were measured refused to participate in the study. from these films. The mechanical axis is defined as the axis of the lower limb with its proximal extremity at Statistical analysis the center of the femoral head and its distal extremity at the center of the ankle. The femoral mechanical A sample size of 30 patients in each group was calcu- lated to detect a difference of 3 degrees between axis is defined by the center of the femoral head and the center of the knee (the center of the knee being groups by the primary endpoint (HKA angle), with the center of the medial shaft in the intercondylar alpha of 0.05 and power of 0.9. From previous studies 4 G. RIVKIN ET AL. we know that standard deviation in postoperative using both CAS and conventional surgical techniques. HKA angle is around 3 degrees, and multiple studies There was no significant difference between both have shown that deviation of 3 degrees is clinically groups regarding post-operative coronal alignment. This was true for overall alignment (HKA) and specific- important [6,10,11]. As we believe the navigation will provide a benefit in this population, we considered a ally for the femoral component and the tibial compo- nent alignment. 3% difference as a conservative estimate. Independent The most common cause for late revision (more samples, two-tailed, t-test was used for comparing dif- than 2 years from index surgery) is aseptic loosening ferent angles between the two groups and a Fischer’s [12]. Finite element analysis studies showed deviations exact test was used for comparing the number of out- from mechanical alignment leads to increased and liers. Significance was assessed at the 0.05 level. Excel asymmetric pressures mainly on the tibial interface software (Microsoft, Redmond Washington) was used which may lead to loosening [10,13]. Fang et al. for statistical analysis. showed increased risk of loosening when the HKA alignment exceeds 2.4 degrees of varus and 7.2 Results degrees of valgus [5]. Computerized assisted surgery (CAS) is considered to improve coronal alignment and Out of 60 surgeries performed, one patient of the reduce the outliers [8,14– 16]. Obese patients have a study group was excluded due to malfunction result- higher risk of developing knee osteoarthritis [17,18]. ing in a wrong distal femur cut, navigation was TKA in these patients is more technically demanding aborted and surgery was completed using conven- with a higher complication rate both intraoperatively tional technique. Data from the navigation pods were such as medial collateral damage and in the early analyzed by the developing team of the manufacturer post-operative period such as wound problems and but the reason for the misguidance was not found, infections [19–21]. Still, other studies show a relation neither in the surgical technique nor in the between higher BMI and poor coronal alignment pods themselves. [7,22]. The combination of increased weight and poor Complete data with good quality x- rays was avail- alignment may cause unbalanced pressure on the able from 57 operations, 29 in the study group and 28 prosthesis-cement-bone interface leading to early loos- in the control group. ening. Therefore, obese patients may prove to be a Data of preoperative and post operative coronal group of patients more likely to benefit from CAS TKA. angles are listed in Table 2. From previous studies, we know that with standard Outliers were defined as angles deviating more instrumentation, the amount of outliers varies and than 3 from the desired 90 in both femur and tibia may be as high as 30% [5,23,24]. coronal alignment. Outliers in the medial distal fem- Although we used computerized randomization the oral angle were seen in 8 patients in the control two groups had slight difference between them. The group compared to 5 in the study group (p¼ 0.358). average age of the control group was 70.1 compared Proximal medial tibial angle outliers were seen in 3 with 66.9 in the study group (p¼ 0.014). There was no patients in the control group and none in the study difference in BMI between the groups (p¼ 0.265). group (p¼ 0.11). There was no difference between the Patients in the control group had a higher pre- two groups in outliers regarding HKA (p> 0.99). operative HKA than patients in the study group (12.3 vs 8.9 ) yet both groups were corrected to a non stat- Discussion istically and clinically significant HKA (2.9 and 2.8 ). Navigated surgical technique increased the mean In our randomized control trial we showed that good surgical time by only 7 min which is not clinically sig- coronal alignment can be achieved in obese patients nificant and was not statistically significant. There are several limitations to our study. The Table 2. Radiographic measurements. power analysis was calculated for the difference in the Study group Control p Value X-rays Analysis 29 28 coronal alignment. With regards to outliers, the groups Preop HKA 8.9 12.3 p¼ 0.005 may have been too small, limiting our ability to reach Post op HKA 2.8 2.9 p¼ 0.87 Mean angle correction 6.1 9.4 p¼ 0.008 statistical significance. Pre op mMDFA 89.9 89.7 p¼ 0.79 We used BMI > 30 as an inclusion criteria and a Post op mMDFA 89.9 89.2 p¼ 0.28 mean BMI of approximately 35. Only 7 patients were Pre op mMPTA 85 84.8 p¼ 0.78 Post op mMPTA 89.8 89.8 p¼ 0.92 morbidly obese with BMI > 40 (5 in the study group COMPUTER ASSISTED SURGERY 5 [4] Winiarsky R, Barth P, Lotke P. Total knee arthroplasty and 2 in the control group) limiting our ability to in morbidly obese patients. J Bone Joint Surg Am. extrapolate conclusions to that very important group 1998;80(12):1770–1774. of patients. [5] Fang DM, Ritter MA, Davis KE. Coronal alignment in In our institute we use bipodal long AP radiographs total knee arthroplasty: just how important is it. J to evaluate HKA. This technique has inherent limita- Arthroplasty. 2009;24(6 Suppl):39–43. [6] Ritter MA, Davis KE, Meding JB, et al. The effect of tions with standardization [25] and also with the alignment and BMI on failure of total knee replace- accuracy of 1 to 2 degrees (Skyta et al.). [26] To over- ment. J Bone Joint Surg Am. 2011;93(17):1588–1596. come this limitation in further studies it would be pru- [7] Estes CS, Schmidt KJ, McLemore R, et al. Effect of dent to use CT scan and EOS (EOS imaging, France) body mass index on limb alignment after total knee This navigation system is useful only with regards arthroplasty. J Arthroplasty. 2013;28(8 Suppl):101–105. to coronal alignment. It lacks the possibility to deter- [8] Chin PL, Yang KY, Yeo SJ, et al. Randomized control trial comparing radiographic total knee arthroplasty mine correct femoral rotation. Determining femoral implant placement using computer navigation versus rotation in our study was done with the conventional conventional technique. J Arthroplasty. 2005;20(5): 3 external rotation. Digital accessories for correct fem- 618–626. oral external rotation position are available. [9] Hirschmann MT, Moser LB, Amsler F, et al. Functional knee phenotypes: a novel classification for phenotyp- ing the coronal lower limb alignment based on the Conclusion native alignment in young non-osteoarthritic patients. Knee Surg Sports Traumatol Arthrosc. 2019;27(5): In obese patients undergoing TKA, good coronal align- 1394–1402. Epub 2019 Apr 11. PMID: 30976825. ment can be achieved both in conventional technique [10] Perillo-Marcone A, Barrett DS, Taylor M. The import- and navigation assisted surgery. The use of navigation ance of tibial alignment: finite element analysis of tib- ial malalignment. J Arthroplasty. 2000;15(8):1020– did not show significant differences in achieving good coronal alignment. [11] Jeffery RS, Morris RW, Denham RA. Coronal alignment after total knee replacement. J Bone Joint Surg Br. 1991;73(5):709–714. Ethical approval [12] Sharkey PF, Lichstein PM, Shen C, et al. Why are total Ethical Review Board: Our institutional review board knee arthroplasties failing today – has anything approved this study changed after 10 years? J Arthroplasty. 2014;29(9): Trial registration ID: CLINCAL TRIAL REGISTRATION 1774–1778. NUMBER: HMO 0092-13 [13] Innocenti B, Bellemans J, Catani F. Deviations from Informed consent was obtained from all patients and ran- optimal alignment in TKA: is there a biomechanical domization then occurred. difference between femoral or tibial component alignment? J Arthroplasty. 2016;31(1):295–301. [14] Bathis H, Perlick L, Tingart M, et al. Alignment in total Disclosure statement knee arthroplasty. J BONE Jt Surg. 2004;86(5):7. [15] Brin YS, Nikolaou VS, Joseph L, et al. Imageless com- No potential conflict of interest was reported by puter assisted versus conventional total knee replace- the author(s). ment. A bayesian meta-analysis of 23 comparative studies. Int Orthop. 2011;35(3):331–339. [16] Chen JY, Chin PL, Tay DKJ, et al. Less outliers in pin- Funding less navigation compared with conventional surgery in total knee arthroplasty. Knee Surg Sports This work was supported by Zimmerbiomet. Traumatol Arthrosc. 2014;22(8):1827–1832. [17] Felson DT, Anderson JJ, Naimark A, et al. Obesity and References knee osteoarthritis. The framingham study. Ann Intern Med. 1988;109(1):18–24. [1] Obesity: preventing and managing the global epi- [18] Coggon D, Reading I, Croft P, et al. Knee osteoarthritis demic. Report of a WHO consultation. World health and obesity. Int J Obes Relat Metab Disord. 2001; organ tech rep ser. 2000. 25(5):622–627. [2] Finkelstein EA, Khavjou OA, Thompson H, et al. [19] Winiarsky R, Barth P, Lotke P. Total knee arthroplasty Obesity and severe obesity forecasts through 2030. in morbidly obese patients. JBJS. 1998;80(12):1770– Am J Prev Med. 2012;42(6):563–570. [3] Singh JA, Gabriel SE, Lewallen DG. Higher body mass [20] Kerkhoffs GMMJ, Servien E, Dunn W, et al. The influ- index is not associated with worse pain outcomes ence of obesity on the complication rate and out- after primary or revision total knee arthroplasty. J come of total knee arthroplasty. J Bone Joint Surg Arthroplasty. 2011;26(3):366–374.e1. Am. 2012;94(20):1839–1844. 6 G. RIVKIN ET AL. € €€ € [21] Jarvenpaa J, Kettunen J, Kroger H, et al. Obesity may [24] Dennis DA, Channer M, Susman MH, et al. impair the early outcome of total knee arthroplasty a Intramedullary versus extramedullary tibial alignment prospective study of 100 patients. Scand J Surg. 2010; systems in total knee arthroplasty. J Arthroplasty. 99(1):45–49. 1993;8(1):43–47. [22] Krushell RJ, Fingeroth RJ. Primary total knee arthro- [25] Cooke TD, Sled EA, Scudamore RA. Frontal plane knee plasty in morbidly obese patients: a 5- to 14-Year fol- alignment: a call for standardized measurement. J low-up study. J Arthroplasty. 2007;22(6 Suppl 2):77–80. Rheumatol. 2007;34(9):1796–1801. € € [23] Mahaluxmivala J, Bankes MJK, Nicolai P, et al. The [26] Skytta ET, Haapamaki V, Koivikko M, et al. effect of surgeon experience on component position- Reliability of the hip-to-ankle radiograph in determin- ing in 673 press fit condylar posterior cruciate- ing the knee and implant alignment after total sacrificing total knee arthroplasties. J Arthroplasty. knee arthroplasty. Acta Orthop Belg. 2011;77(3):329– 2001;16(5):635–640. 335.
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Total knee arthroplasty using a computerized assisted stereotaxic navigation system with bluetooth communication in obese patients - A randomized controlled study
Total knee arthroplasty using a computerized assisted stereotaxic navigation system with bluetooth communication in obese patients - A randomized controlled study
Abstract
Abstract Correct mechanical alignment (180° hip-knee-angle (HKA)) may be difficult to obtain on a consistent basis in obese patients. This is a randomized controlled study comparing the post-operative coronal alignment in obese patients between two surgical total knee arthroplasty (TKA) techniques – conventional and computer assisted navigation. The primary outcome was the post-operative HKA. A total of 60 patients were assigned to undergo conventional total knee arthroplasty (30...
COMPUTER ASSISTED SURGERY 2023, VOL. 28, NO. 1, 2162970 https://doi.org/10.1080/24699322.2022.2162970 RESEARCH ARTICLE Total knee arthroplasty using a computerized assisted stereotaxic navigation system with bluetooth communication in obese patients - A randomized controlled study a a a b a a Gurion Rivkin , Leonid Kandel , Itay Perets , Tamir Tsohar , Tarek Nasrawy and Meir Liebergall a b Department of Orthopedics, Hadassah Hebrew University Hospital, Jerusalem, Israel; Department of Physiotherapy and Rehabilitation, Hadassah Hebrew University Hospital, Jerusalem, Israel KEYWORDS ABSTRACT Total knee arthroplasty; Correct mechanical alignment (180 hip-knee-angle (HKA)) may be difficult to obtain on a con- obese; coronal alignment; sistent basis in obese patients. This is a randomized controlled study comparing the post-opera- navigation; prospective tive coronal alignment in obese patients between two surgical total knee arthroplasty (TKA) randomized trial techniques – conventional and computer assisted navigation. The primary outcome was the post-operative HKA. A total of 60 patients were assigned to undergo conventional total knee arthroplasty (30 patients) or computerized assisted stereotaxic navigation system with Bluetooth communication surgery (30 patients). One patient from the study group was excluded due to malfunction of the navigation system. Good quality x-rays were available in 57 patients. There was no difference between the groups. Post-operative HKA was 2.8 and 2.9 in the study and control groups, respectively (p¼ 0.87). In obese patients undergoing TKA, computerized naviga- tion had no impact on post-op HKA. Clincal Trial Registration Number: HMO 0092-13 Introduction The use of navigation systems in TKA have been shown to improve alignment and significantly reduce Obesity was declared a global epidemic in 2000 by outliers [8]. Thus, in this randomized controlled study, the World Health Organization, affecting both devel- the main aim was to compare the coronal radiological oped and developing countries regardless of socioeco- outcome of implant placement in obese patients (BMI nomic levels [1]. It is estimated that in the year 2030 > 30) using computerized assisted stereotaxic naviga- at least 40% of the US population will be obese (BMI tion system with Bluetooth communication versus >30), and greater than 10% will be severely obese conventional instrumentation in total knee arthro- (BMI > 40) [2]. The combination of aging population plasty. We hypothesized that the use of CAS would with obesity epidemic will lead to an increased inci- achieve better coronal alignment in obese patients. dence of knee osteoarthritis in obese patients. Although post-operative results of knee arthroplasty Material and methods may be similar for patients with high BMI [3], they are at increased risk of complications such as wound com- After obtaining approval from the ethical committee, plications, infection and medial collateral injury [4]. we performed a randomized, controlled trial that com- Long-term survival of TKA may be related to correct pared CAS to conventional instrumentation in patients prosthesis and knee alignment [5]. Correct alignment who underwent primary TKA. Sixty patients were may be more difficult to achieve in obese patients, enrolled; the study group consisted of 30 patients that where some of the anatomic landmarks are obscured underwent TKA with a computerized assisted stereo- by fatty soft tissue. Several studies showed the rela- taxic navigation system with Bluetooth communication tion between increased BMI and malalignment causing - the iAssistV Knee System (Zimmer Biomet CAS, increased risk of failure [5–7]. Montreal, Canada), and 30 control patients that CONTACT Gurion Rivkin gurion@hadassah.org.il Department of Orthopedics, Hadassah Hebrew University Hospital, Jerusalem, Israel 2023 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 2 G. RIVKIN ET AL. underwent TKA with conventional instrumentation. In Surgical technique V R both groups the Persona (Zimmer Biomet, Warsaw, All surgeries were performed by one of four surgeons IN) knee prosthesis was used. well versed in the navigation system. (GR, YM, LK Inclusion criteria were patients that underwent pri- and ML). mary TKA for the treatment of non-inflammatory Regional anesthesia was used in 50 patients and degenerative joint disease, over 18 years old, and BMI general anesthesia in 10 patients (Table 1). 30. Exclusion Criteria were active infection, severe In all arthroplasties, a medial parapatellar approach hip arthrosis, neurological and vascular disorders, pre- was used under tourniquet without patella eversion. vious ipsilateral knee surgery, hip or knee ankyloses, Patellae were not resurfaced. A posterior cruciate sacri- collateral ligament insufficiency and cancer. ficing knee implant was used in all cases. The study workflow is depicted in the attached The surgical technique of the study group consisted CONSORT flow chart (Figure 1). of navigated distal femoral and proximal tibia cuts. In Patients who had appropriate indication to the femoral side, the point of entry to the medullary be candidates for TKA and who met the specified inclusion and exclusion criteria, were informed Table 1. Study demographics. about the CAS and offered entry into the study. Study group Control p Value Informed consent was obtained from all patients Age 66.9 70.1 p¼ 0.014 Gender (female : male) 21:9 19:11 p¼ 0.58 and randomization then occurred. The randomization BMI 35.6 34.4 p¼ 0.265 process is discussed further under the randomiza- Anesthesia (regional : general) 25 : 5 25:5 p> 0.999 Surgery time 77 70 p¼ 0.098 tion procedure. Figure 1. The study workflow chart. COMPUTER ASSISTED SURGERY 3 canal was identified and a short rod was attached to it notch of the femur or femoral component). The tibial without piercing the medullary canal. A position sen- mechanical axis is defined by the center of the ankle sor (pod) was attached to the rod and a conical shape and the middle of the tibia plateau. movement of the thigh allowed the navigated system The study endpoints consisted of several different to identify the physiological femoral center of rotation. angles which were monitored to evaluate the lower A second pod was then attached to a cutting guide limb alignment. They are as follows: assembly and a perpendicular plane to the coronal mechanical axis was identified. The aim was for a dis- Primary outcomes The hip-knee-ankle (HKA) angle – the angle between tal femoral cut perpendicular to the mechanical axis the femoral and tibial mechanical axis. The primary cri- with 3 degrees of flexion in the sagittal plane. The rest of the femoral preparation was completed with a terion is that HKA should be in the range 180 ±3 , 4-in-1 technique setting external rotation at 3 degrees which is considered a correct position of the prosthesis. compared to the posterior condylar axis. For the tibial proximal cut an extramedullary type construct with a Secondary outcomes pod connected to it was attached to the malleoli and For easier calculations we used mechanical medial the tibial surface over the PCL attachment point. femoral distal angle (mMDFA), as described by Medial and lateral movement of the knee was used to Hirschmann et al. [9] the medial angle formed set the tibial mechanical alignment. A cutting guide between the mechanical femoral axis and the axis apparatus was attached to the proximal tibia medial to the tibial tubercle with a second pod connected. connecting most distal points of the medial and lateral femoral condyles. After the mechanical alignment was obtained the first Mechanical medial proximal tibial angle (mMPTA) – pod was also attached to the cutting guide assembly with an aim of a cut perpendicular to the coronal the medial angle formed between the mechanical tib- mechanical axis with a 3 degrees posterior slope in ial axis and the tibial tangent in the native knee. In the operated knee the tibial proximal angle is formed the sagittal plane. Conventional surgical technique consisted of an by the mechanical axis and the axis of the lower bor- intramedullary femoral alignment jig set at 5 degrees der of the tibial tray. valgus cut and extramedullary tibial alignment aimed at 90 degrees coronal plane cut and a 3 degrees pos- Randomization procedure terior slope in the sagittal plane. A random number series was generated and assigned The tourniquet was deflated after skin closure. with a unique number. Envelopes labeled with the All patients were treated with low molecular weight patient’s randomization number contained a sticker heparin (LMWH) 40 mg daily from post-operative day inside identifying the randomization group. The sur- (POD) 1. Full weight bearing was encouraged with a plan for home discharge. geon was provided with the envelopes and instruc- tions for using them before the start of the study. Prior to surgery, the envelope that contained the Radiographic measurements patient’s randomization number and treatment assign- Full-length standing anteroposterior radiographs were ment to one of the two groups – either the study group collected from all patients pre-operatively and at or the control group. The randomization envelopes were 6-weeks post-operatively. All x-rays collected were per- used in sequential order of patient enrollment. st th formed with the same technique of bipodal standing Between June 1 2015 and January 25 2017 a with no hip rotation and patella facing forward. The total of 508 TKAs were performed. Of these, 253 had a change in alignment of the knee and the position of BMI > 30. Sixty-four patients were excluded and 129 the tibial and femoral components were measured refused to participate in the study. from these films. The mechanical axis is defined as the axis of the lower limb with its proximal extremity at Statistical analysis the center of the femoral head and its distal extremity at the center of the ankle. The femoral mechanical A sample size of 30 patients in each group was calcu- lated to detect a difference of 3 degrees between axis is defined by the center of the femoral head and the center of the knee (the center of the knee being groups by the primary endpoint (HKA angle), with the center of the medial shaft in the intercondylar alpha of 0.05 and power of 0.9. From previous studies 4 G. RIVKIN ET AL. we know that standard deviation in postoperative using both CAS and conventional surgical techniques. HKA angle is around 3 degrees, and multiple studies There was no significant difference between both have shown that deviation of 3 degrees is clinically groups regarding post-operative coronal alignment. This was true for overall alignment (HKA) and specific- important [6,10,11]. As we believe the navigation will provide a benefit in this population, we considered a ally for the femoral component and the tibial compo- nent alignment. 3% difference as a conservative estimate. Independent The most common cause for late revision (more samples, two-tailed, t-test was used for comparing dif- than 2 years from index surgery) is aseptic loosening ferent angles between the two groups and a Fischer’s [12]. Finite element analysis studies showed deviations exact test was used for comparing the number of out- from mechanical alignment leads to increased and liers. Significance was assessed at the 0.05 level. Excel asymmetric pressures mainly on the tibial interface software (Microsoft, Redmond Washington) was used which may lead to loosening [10,13]. Fang et al. for statistical analysis. showed increased risk of loosening when the HKA alignment exceeds 2.4 degrees of varus and 7.2 Results degrees of valgus [5]. Computerized assisted surgery (CAS) is considered to improve coronal alignment and Out of 60 surgeries performed, one patient of the reduce the outliers [8,14– 16]. Obese patients have a study group was excluded due to malfunction result- higher risk of developing knee osteoarthritis [17,18]. ing in a wrong distal femur cut, navigation was TKA in these patients is more technically demanding aborted and surgery was completed using conven- with a higher complication rate both intraoperatively tional technique. Data from the navigation pods were such as medial collateral damage and in the early analyzed by the developing team of the manufacturer post-operative period such as wound problems and but the reason for the misguidance was not found, infections [19–21]. Still, other studies show a relation neither in the surgical technique nor in the between higher BMI and poor coronal alignment pods themselves. [7,22]. The combination of increased weight and poor Complete data with good quality x- rays was avail- alignment may cause unbalanced pressure on the able from 57 operations, 29 in the study group and 28 prosthesis-cement-bone interface leading to early loos- in the control group. ening. Therefore, obese patients may prove to be a Data of preoperative and post operative coronal group of patients more likely to benefit from CAS TKA. angles are listed in Table 2. From previous studies, we know that with standard Outliers were defined as angles deviating more instrumentation, the amount of outliers varies and than 3 from the desired 90 in both femur and tibia may be as high as 30% [5,23,24]. coronal alignment. Outliers in the medial distal fem- Although we used computerized randomization the oral angle were seen in 8 patients in the control two groups had slight difference between them. The group compared to 5 in the study group (p¼ 0.358). average age of the control group was 70.1 compared Proximal medial tibial angle outliers were seen in 3 with 66.9 in the study group (p¼ 0.014). There was no patients in the control group and none in the study difference in BMI between the groups (p¼ 0.265). group (p¼ 0.11). There was no difference between the Patients in the control group had a higher pre- two groups in outliers regarding HKA (p> 0.99). operative HKA than patients in the study group (12.3 vs 8.9 ) yet both groups were corrected to a non stat- Discussion istically and clinically significant HKA (2.9 and 2.8 ). Navigated surgical technique increased the mean In our randomized control trial we showed that good surgical time by only 7 min which is not clinically sig- coronal alignment can be achieved in obese patients nificant and was not statistically significant. There are several limitations to our study. The Table 2. Radiographic measurements. power analysis was calculated for the difference in the Study group Control p Value X-rays Analysis 29 28 coronal alignment. With regards to outliers, the groups Preop HKA 8.9 12.3 p¼ 0.005 may have been too small, limiting our ability to reach Post op HKA 2.8 2.9 p¼ 0.87 Mean angle correction 6.1 9.4 p¼ 0.008 statistical significance. Pre op mMDFA 89.9 89.7 p¼ 0.79 We used BMI > 30 as an inclusion criteria and a Post op mMDFA 89.9 89.2 p¼ 0.28 mean BMI of approximately 35. Only 7 patients were Pre op mMPTA 85 84.8 p¼ 0.78 Post op mMPTA 89.8 89.8 p¼ 0.92 morbidly obese with BMI > 40 (5 in the study group COMPUTER ASSISTED SURGERY 5 [4] Winiarsky R, Barth P, Lotke P. Total knee arthroplasty and 2 in the control group) limiting our ability to in morbidly obese patients. J Bone Joint Surg Am. extrapolate conclusions to that very important group 1998;80(12):1770–1774. of patients. [5] Fang DM, Ritter MA, Davis KE. Coronal alignment in In our institute we use bipodal long AP radiographs total knee arthroplasty: just how important is it. J to evaluate HKA. This technique has inherent limita- Arthroplasty. 2009;24(6 Suppl):39–43. [6] Ritter MA, Davis KE, Meding JB, et al. The effect of tions with standardization [25] and also with the alignment and BMI on failure of total knee replace- accuracy of 1 to 2 degrees (Skyta et al.). [26] To over- ment. J Bone Joint Surg Am. 2011;93(17):1588–1596. come this limitation in further studies it would be pru- [7] Estes CS, Schmidt KJ, McLemore R, et al. Effect of dent to use CT scan and EOS (EOS imaging, France) body mass index on limb alignment after total knee This navigation system is useful only with regards arthroplasty. J Arthroplasty. 2013;28(8 Suppl):101–105. to coronal alignment. It lacks the possibility to deter- [8] Chin PL, Yang KY, Yeo SJ, et al. Randomized control trial comparing radiographic total knee arthroplasty mine correct femoral rotation. Determining femoral implant placement using computer navigation versus rotation in our study was done with the conventional conventional technique. J Arthroplasty. 2005;20(5): 3 external rotation. Digital accessories for correct fem- 618–626. oral external rotation position are available. [9] Hirschmann MT, Moser LB, Amsler F, et al. Functional knee phenotypes: a novel classification for phenotyp- ing the coronal lower limb alignment based on the Conclusion native alignment in young non-osteoarthritic patients. Knee Surg Sports Traumatol Arthrosc. 2019;27(5): In obese patients undergoing TKA, good coronal align- 1394–1402. Epub 2019 Apr 11. PMID: 30976825. ment can be achieved both in conventional technique [10] Perillo-Marcone A, Barrett DS, Taylor M. The import- and navigation assisted surgery. The use of navigation ance of tibial alignment: finite element analysis of tib- ial malalignment. J Arthroplasty. 2000;15(8):1020– did not show significant differences in achieving good coronal alignment. [11] Jeffery RS, Morris RW, Denham RA. Coronal alignment after total knee replacement. J Bone Joint Surg Br. 1991;73(5):709–714. Ethical approval [12] Sharkey PF, Lichstein PM, Shen C, et al. Why are total Ethical Review Board: Our institutional review board knee arthroplasties failing today – has anything approved this study changed after 10 years? J Arthroplasty. 2014;29(9): Trial registration ID: CLINCAL TRIAL REGISTRATION 1774–1778. NUMBER: HMO 0092-13 [13] Innocenti B, Bellemans J, Catani F. Deviations from Informed consent was obtained from all patients and ran- optimal alignment in TKA: is there a biomechanical domization then occurred. difference between femoral or tibial component alignment? J Arthroplasty. 2016;31(1):295–301. [14] Bathis H, Perlick L, Tingart M, et al. Alignment in total Disclosure statement knee arthroplasty. J BONE Jt Surg. 2004;86(5):7. [15] Brin YS, Nikolaou VS, Joseph L, et al. Imageless com- No potential conflict of interest was reported by puter assisted versus conventional total knee replace- the author(s). ment. A bayesian meta-analysis of 23 comparative studies. Int Orthop. 2011;35(3):331–339. [16] Chen JY, Chin PL, Tay DKJ, et al. Less outliers in pin- Funding less navigation compared with conventional surgery in total knee arthroplasty. Knee Surg Sports This work was supported by Zimmerbiomet. Traumatol Arthrosc. 2014;22(8):1827–1832. [17] Felson DT, Anderson JJ, Naimark A, et al. Obesity and References knee osteoarthritis. The framingham study. Ann Intern Med. 1988;109(1):18–24. [1] Obesity: preventing and managing the global epi- [18] Coggon D, Reading I, Croft P, et al. Knee osteoarthritis demic. Report of a WHO consultation. World health and obesity. Int J Obes Relat Metab Disord. 2001; organ tech rep ser. 2000. 25(5):622–627. [2] Finkelstein EA, Khavjou OA, Thompson H, et al. [19] Winiarsky R, Barth P, Lotke P. Total knee arthroplasty Obesity and severe obesity forecasts through 2030. in morbidly obese patients. JBJS. 1998;80(12):1770– Am J Prev Med. 2012;42(6):563–570. [3] Singh JA, Gabriel SE, Lewallen DG. Higher body mass [20] Kerkhoffs GMMJ, Servien E, Dunn W, et al. The influ- index is not associated with worse pain outcomes ence of obesity on the complication rate and out- after primary or revision total knee arthroplasty. J come of total knee arthroplasty. J Bone Joint Surg Arthroplasty. 2011;26(3):366–374.e1. Am. 2012;94(20):1839–1844. 6 G. RIVKIN ET AL. € €€ € [21] Jarvenpaa J, Kettunen J, Kroger H, et al. Obesity may [24] Dennis DA, Channer M, Susman MH, et al. impair the early outcome of total knee arthroplasty a Intramedullary versus extramedullary tibial alignment prospective study of 100 patients. Scand J Surg. 2010; systems in total knee arthroplasty. J Arthroplasty. 99(1):45–49. 1993;8(1):43–47. [22] Krushell RJ, Fingeroth RJ. Primary total knee arthro- [25] Cooke TD, Sled EA, Scudamore RA. Frontal plane knee plasty in morbidly obese patients: a 5- to 14-Year fol- alignment: a call for standardized measurement. J low-up study. J Arthroplasty. 2007;22(6 Suppl 2):77–80. Rheumatol. 2007;34(9):1796–1801. € € [23] Mahaluxmivala J, Bankes MJK, Nicolai P, et al. The [26] Skytta ET, Haapamaki V, Koivikko M, et al. effect of surgeon experience on component position- Reliability of the hip-to-ankle radiograph in determin- ing in 673 press fit condylar posterior cruciate- ing the knee and implant alignment after total sacrificing total knee arthroplasties. J Arthroplasty. knee arthroplasty. Acta Orthop Belg. 2011;77(3):329– 2001;16(5):635–640. 335.
Higher body mass index is not associated with worse pain outcomes after primary or revision total knee arthroplasty
Total knee arthroplasty in morbidly obese patients
Coronal alignment in total knee arthroplasty: just how important is it
The effect of alignment and BMI on failure of total knee replacement
Effect of body mass index on limb alignment after total knee arthroplasty
Randomized control trial comparing radiographic total knee arthroplasty implant placement using computer navigation versus conventional technique
Functional knee phenotypes: a novel classification for phenotyping the coronal lower limb alignment based on the native alignment in young non-osteoarthritic patients
The importance of tibial alignment: finite element analysis of tibial malalignment
Coronal alignment after total knee replacement
Why are total knee arthroplasties failing today – has anything changed after 10 years?
Deviations from optimal alignment in TKA: is there a biomechanical difference between femoral or tibial component alignment?
Alignment in total knee arthroplasty
Imageless computer assisted versus conventional total knee replacement. A bayesian meta-analysis of 23 comparative studies
Less outliers in pinless navigation compared with conventional surgery in total knee arthroplasty
Obesity and knee osteoarthritis. The framingham study
Knee osteoarthritis and obesity
Total knee arthroplasty in morbidly obese patients
The influence of obesity on the complication rate and outcome of total knee arthroplasty
Obesity may impair the early outcome of total knee arthroplasty a prospective study of 100 patients
Primary total knee arthroplasty in morbidly obese patients: a 5- to 14-Year follow-up study
The effect of surgeon experience on component positioning in 673 press fit condylar posterior cruciate-sacrificing total knee arthroplasties
Intramedullary versus extramedullary tibial alignment systems in total knee arthroplasty
Frontal plane knee alignment: a call for standardized measurement
Reliability of the hip-to-ankle radiograph in determining the knee and implant alignment after total knee arthroplasty
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