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Factors affecting the incidence and management of fixed flexion deformity in total knee arthroplasty: A systematic review
THEKNE-02601; No of Pages 8 The Knee xxx (2018) xxx–xxx
Contents lists available at ScienceDirect
The Knee
Review
Factors affecting the incidence and management of fixed flexion deformity in total knee arthroplasty: A systematic review Vincent V.G. An a,b,⁎, Corey J. Scholes a, Brett A. Fritsch a,c a b c
Sydney Orthopaedic Research Institute, Chatswood, NSW 2067, Australia Sydney Medical School, University of Sydney, Camperdown, NSW 2050, Australia Department of Orthopaedics, Royal Prince Alfred Hospital, Camperdown, NSW, Australia
a r t i c l e
i n f o
Article history: Received 1 December 2017 Received in revised form 11 December 2017 Accepted 11 March 2018 Available online xxxx Keywords: Knee Arthroplasty Fixed flexion deformity Systematic review
a b s t r a c t Purpose: This study aimed to systematically review the literature and identify factors which would contribute to the intraoperative correction of FFD to frame a potential surgical algorithm or predictive model to guide intraoperative decision-making. Methods: Electronic searches of six databases were undertaken in April 2016 according to the PRISMA guidelines, and the reference lists of studies searched. Quality of studies was assessed using the STROBE checklist, and the Downs and Black Scores. Results: Twenty-five studies investigating 10, 679 knees were found to satisfy the inclusion and exclusion criteria. These studies described a variety of pre-operative and intra-operative factors which contribute to the development or correction of post-operative FFD. The only patient predictor of post-operative FFD was pre-operative FFD. The intra-operative steps described to correct FFD were: distal femoral resection, soft-tissue balancing (in the posterior and medial compartments), sagittal component flexion and posterior condylar offset. However, no studies investigated these in an integrated model. Conclusion: This review has identified various pre-, intra- and post-operative factors predictive of post-operative FFD. In practice, these factors are likely to interact, and therefore further investigation in an integrated model is crucial to developing a statistically sound and reliable intraoperative algorithm for surgeons to follow when correcting fixed flexion deformity. © 2018 Elsevier B.V. All rights reserved.
Contents 1. 2.
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Introduction . . . . . . . . . . . . . . . . . Methods . . . . . . . . . . . . . . . . . . . 2.1. Literature search . . . . . . . . . . . . 2.2. Selection criteria . . . . . . . . . . . . 2.3. Quality appraisal . . . . . . . . . . . . 2.4. Data extraction . . . . . . . . . . . . 2.5. Data analysis . . . . . . . . . . . . . Results . . . . . . . . . . . . . . . . . . . 3.1. Search results . . . . . . . . . . . . . 3.1.1. Article methodology and designs
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⁎ Corresponding author at: Sydney Orthopaedic Research Institute, Level 1, The Gallery, 445 Victoria Ave, Chatswood, NSW 2067, Australia. E-mail address: [email protected] (V.V.G. An).
https://doi.org/10.1016/j.knee.2018.03.008 0968-0160/© 2018 Elsevier B.V. All rights reserved.
Please cite this article as: An VVG, et al, Factors affecting the incidence and management of fixed flexion deformity in total knee arthroplasty: A systematic review, Knee (2018), https://doi.org/10.1016/j.knee.2018.03.008
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3.2. 3.3.
Quality of studies . . . . . . Findings of studies . . . . . 3.3.1. Patient factors . . . 3.3.2. Single operative steps 3.3.3. Surgical algorithms . 4. Discussion . . . . . . . . . . . . . 5. Conclusion . . . . . . . . . . . . Acknowledgements . . . . . . . . . . . References . . . . . . . . . . . . . . .
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1. Introduction In traditional mechanically aligned (MA) total knee arthroplasty (TKA), a key objective is to restore the mechanical axis (MA) of the knee in extension in both coronal and sagittal planes. A maximally extended knee that remains in considerable flexion (fixed flexion deformity or FFD) is observed in up to 17% of knees following TKA [1]. Post-operative FFD is associated with abnormal gait requiring excessive energy expenditure and quadriceps loading [2], with an increased risk of anterior knee pain, reduced function and a reduction in patient reported outcome scores [3]. Post-operative extension has been correlated with intraoperative range of motion [4], therefore the intraoperative correction of FFD in TKA is a key surgical outcome. Historically, FFD has been managed in an empirical manner via surgical algorithms which revolve around ligament balancing, releases and further distal resection if necessary. For example, Bellemans et al. proposed a four-step algorithm comprising osteophyte removal and ligament balancing, followed by transverse posterior capsular release, then distal femoral over-resection and finally tenotomy of the knee flexors [5], progressing to each successive step only if FFD was remaining. Although the success of published surgical algorithms is well-described [5–11], they involve a subsequent re-resection of the distal femur, which prolongs operative duration whilst resetting the cutting guides, increasing the risk of excessive bleeding, infection [12] and deep vein thrombosis [13]. Femoral recuts can be difficult to make accurately with all systems, and they result in a change in the joint line. The combination of a delayed surgical work flow, and concerns around accuracy, makes it desirable to be able to predict the distal femoral resection to achieve full extension in all deformities, prior to making the first femoral cut. A predictive model able to dictate the appropriate surgical steps to be undertaken to correct FFD in any given patient with the least number of operative steps would aid the pre-operative surgical planning process, leading to streamlined intraoperative decision making and reduced operative time. To develop such a model, a detailed understanding of all the factors involved in the development and intraoperative prevention of post-TKR FFD is required. The pre-operative characteristics which predispose patients to developing post-operative FFD should be identified and the contribution of each individual operative step to correcting FFD needs to be quantified. Once determined, these factors can be subject to multivariate regression analysis to develop an accurate and validated predictive model for achieving full extension [14]. This data-driven approach is a considerable departure from the previous empirical approach to FFD correction. The purpose of this systematic review was to identify those factors predisposing patients to post-operative FFD, as well as factors involved in the intraoperative correction of FFD, with the intention of proposing a predictive model to guide intraoperative decision-making. 2. Methods 2.1. Literature search This review was registered on the PROSPERO database (CRD42016037207). A systematic review of the literature was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [15]. Electronic searches were performed in the Ovid MEDLINE, PubMed, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, ACP Journal Club, and Database of Abstracts of Review of Effectiveness during April 2016. To achieve maximum sensitivity, the terms (“flexion contracture” OR “flexion deformity”) AND (“knee arthroplasty” OR “knee replacement”) were combined as keywords. The reference lists of retrieved articles were reviewed to identify any additional relevant studies as per the inclusion and exclusion criteria as listed below. 2.2. Selection criteria Studies eligible for this systematic review included English-language studies published at any time that addressed or reported pre-operative or intra-operative factors in total knee arthroplasty for osteoarthritis that affect post-operative fixed flexion deformity. Specifically, studies investigating pre-operative and intra-operative factors were included. Studies investigating rheumatoid arthritis or haemophiliac arthropathy were excluded. Case reports, abstracts and conference proceedings were also excluded. Please cite this article as: An VVG, et al, Factors affecting the incidence and management of fixed flexion deformity in total knee arthroplasty: A systematic review, Knee (2018), https://doi.org/10.1016/j.knee.2018.03.008
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2.3. Quality appraisal The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) was used to evaluate the structure, quality and reporting of studies [16]. Study design was classified using the NHMRC level of evidence grading. Further to this, the studies were appraised using the Downs and Black score [17]. 2.4. Data extraction Data regarding factors or strategies affecting the development or prevention of post-TKR FFD were extracted from the text, figures and tables of included references. The effect of each predictor on FFD post-TKR at any time-point was recorded. 2.5. Data analysis Due to heterogeneity in study designs and reporting methods, meta-analysis of outcomes could not be performed. The included studies were divided into three main categories based on the factors investigated: pre-operative factors, surgical steps and surgical algorithms. Pre-operative factors were variables that were associated with patients developing post-operative TKR. Surgical steps were individual measures employed intraoperatively to correct FFD and prevent the incidence of post-operative FFD. Studies investigating surgical algorithms assessed the success of sequences involving particular intraoperative steps employed to correct and prevent post-operative FFD. FFD as an endpoint was defined as deficit in extension range of motion measured at any time during the intra- or post-operative period. 3. Results 3.1. Search results The initial search yielded 433 articles. Title and abstract screening left 55 articles for full-text review. After applying the inclusion and exclusion criteria, 21 studies [3,5–11,18–30] were retained for further analysis. After searching the reference lists of the included articles a further four references [4, 31–33] were acquired for inclusion, leaving a total of 25 studies for further analysis (Figure 1). 3.1.1. Article methodology and designs Included studies employed a variety of designs, measurement techniques for extension range of motion and length of followup (Table 1). The literature search retrieved one randomised controlled trial, 20 cohort studies, three case–control studies and one cadaveric study. Knee range of motion was assessed at various time-points from immediately intraoperatively to beyond 72 months. Goniometers were used in 16 studies: two studies used computer navigation, three used radiographs, one study used intraoperative photographs and skin markers, whilst three did not report their method of assessment. Time of assessment ranged from measurements taken intraoperatively to measurements taken at a mean of 70 months, with a maximum of 120 months' follow-up (see Table 1). 3.2. Quality of studies The quality of included studies was determined by their NHMRC level of evidence. Only one study was level II, whilst 10 were level III studies, and 14 were level IV studies. The median Downs and Black score was 17 out of a possible 26 points (Range: 14–22). The components of the Downs and Black score most poorly satisfied were related to: – Item 12: were the participants representative of the entire population? – Item 15: was an attempt made to blind the measurement of the outcome? – Item 23: were study subjects randomised to intervention groups? – Item 24: was the randomised intervention concealed from patients and healthcare until recruitment was complete and irrevocable? 3.3. Findings of studies The included studies investigated a total of 10,679 knees. Papers investigated a variety of pre-operative factors, isolated intraoperative steps and the success of described surgical algorithms in correcting FFD. The identified factors are displayed by time in Figure 2. 3.3.1. Patient factors Five of the included studies [3,18–20,24] correlated pre-operative patient factors with the incidence of post-operative fixed flexion deformity. The factors predictive of post-operative FFD were male sex, increased age, and pre-operative FFD. The role of sex and age in the development of post-operative FFD is unclear. Goudie et al. directly compared the demographics of patients with less than five degree post-operative FFD and those with greater than five degree FFD at a mean of two years post-operatively and found that the proportion of males and mean age were significantly greater in patients with the N 5 degree FFD group (p = 0.01, p = 0.02) [18]. Please cite this article as: An VVG, et al, Factors affecting the incidence and management of fixed flexion deformity in total knee arthroplasty: A systematic review, Knee (2018), https://doi.org/10.1016/j.knee.2018.03.008
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Figure 1. PRISMA flow chart demonstrating the article search and retrieval process.
A later study by Lustig et al. contradicted this notion, finding no significant difference between patients with and without at least five degree FFD at the one-year post-operative mark in terms of gender or age [24]. On the other hand, the role of pre-operative FFD in the development of post-operative FFD is unanimous. Goudie et al. compared patients with and without post-operative FFD and found that the degree of pre-operative FFD was significantly greater in the group with post-operative FFD at 24 months [18]. Furthermore, Koh et al. via multivariable analysis found that every five degrees of preoperative FFD conferred a 1.7 times risk of post-operative FFD at an average of 35 months of follow-up, whilst Ritter et al. found that at a minimum of 72 months of follow-up, having a pre-operative FFD of between 20 and 50° conferred a 5.8 times risk of developing post-operative FFD, and one of five to 19° conferred a 2.9 times risk [3,19].
3.3.2. Single operative steps For those patients presenting with an FFD, included studies also investigated the effect of individual operative steps on FFD. In particular, the role of distal femoral resection, femoral component flexion, and soft-tissue balancing was investigated.
3.3.2.1. Distal femoral resection. Distal femoral resection has been examined by four separate groups [4,22,23,29], showing that greater resection of the distal femur restores a greater degree of extension. Using cadavers, Cross et al. investigated the effect of sequential two millimetre resections of the distal femur in excess of the thickness of the femoral implant (nine millimetres) on extension intraoperatively, and found that the first two millimetre resection brought the mean maximum extension from 9.7° of flexion to 6.4°, and a further two millimetres brought the mean Please cite this article as: An VVG, et al, Factors affecting the incidence and management of fixed flexion deformity in total knee arthroplasty: A systematic review, Knee (2018), https://doi.org/10.1016/j.knee.2018.03.008
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Table 1 Details of the study design, measurement techniques employed, follow-up period and Downs and Black score of the included studies. Author
Year
Design
Measurement technique
Time of post-op measurement
Downs and Black score
Bellemans Berend Firestone Jain Meftah Mihalko Whiteside Goudie Koh Lustig Ritter Schurman Bin Abd Razak Cross McAllister Nagai Okamoto Onodera Smith Zhang Bengs Gatha Chaudhary Liu Asano
2006 2006 1992 2013 2012 2003 2002 2011 2013 2012 2007 1985 2014 2012 2008 2015 2014 2013 2010 2008 2006 2004 2008 2016 2008
Cohort Cohort Cohort Cohort Cohort Cohort Cohort Case control Case control Case control Cohort Cohort Cohort Cadaver Cohort Cohort Cohort Cohort Cohort Cohort Cohort Cohort RCT Cohort Cohort
Goniometer Goniometer Goniometer Goniometer NR NR Goniometer Goniometer Goniometer Goniometer Goniometer Goniometer Goniometer Praxim Navigation Goniometer Radiographs Radiographs NR Photographs with skin markers Radiographs Goniometer Goniometer Goniometer Navigation Goniometer
24 months 38 months (1.6–77 months) 53 months (26–84 months) 12 months 3.1 years (1.7–4.9 years) 70 months (12–120 months) 24 months 24 months 35 months (24–72 months) 12 months At least 72 months 24 months 24 months Intraoperative 12 months 4 weeks 12 months NR Intraoperative 12 months Intraoperative 51 months (24–72 months) 24 months Intraoperative 12 months
18 17 15 14 16 16 17 17 18 18 17 15 17 22 20 19 20 16 20 15 21 16 22 21 14
FFD to 1.4° [22]. They proposed the “2 by 4” rule, which approximates that for every two millimetres of distal femoral resection, four degrees of FFD is corrected. Bengs and Scott, Smith et al. and Liu et al. used different approaches to assess the effect of distal femoral resection on extension [4,23,29]. Using augments with increasing thickness to mimic the effect of “excess” distal femur on FFD intraoperatively, Smith et al. found that for every two millimetres of bone resected, approximately 3.6° of extension was restored, whilst Liu et al. found that with the first two millimetres of distal femoral (DF) resection, 3.36° was restored. Both studies were in agreeance with Cross et al.'s findings. Meanwhile, Bengs et al. found that for every two millimetres of bone resected, nine degrees of passive extension could be restored. 3.3.2.2. Femoral component sagittal placement. The literature on the effect of the sagittal placement of the femoral component is sparse, with only two studies [24,30] having investigated the role of femoral component flexion on post-operative FFD at 12 months. Zhang et al. found that TKAs with femoral component flexion had a decreased extension range of motion at 12 months compared to those without, although it was not reported what constituted a femoral component being in flexion [30]. Furthermore, the method of measuring the range of motion was not reported. Lustig et al. subsequently investigated this relationship, and found that knees with greater than 3.5° of component flexion (as assessed by computer navigation) had a greater proportion of one year post-operative FFD (greater than five degrees) compared to those without component flexion [24].
Figure 2. Factors which affect fixed flexion deformity intraoperatively and during post-operative recovery.
Please cite this article as: An VVG, et al, Factors affecting the incidence and management of fixed flexion deformity in total knee arthroplasty: A systematic review, Knee (2018), https://doi.org/10.1016/j.knee.2018.03.008
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Table 2 Description of studies using algorithms to correct fixed flexion deformity, and the steps taken to correct this deformity. Author and year
Steps in algorithm
Bellemans 2006
1. Coronal balancing with osteophytes and 2 mm DF resection. 2. Posterior capsular and gastrocnemius release. 3. DF resection up to 4 mm. 4. Hamstring tenotomy 1. Osteophyte removal, 2. DF resection, 3. PCL release, 4. DF re-resection to 4 mm, soft tissue releases. 1. Osteophyte and loose body removal. 2. Additional DF resection. 3. Soft tissue release in extension and flexion (posteromedial in varus knees, and posterolateral in valgus knees) If less than 30°: 1. Osteophyte removal. 2. Posterior capsular release. 3. Release of collateral ligaments. 4. 2 mm DF re-resection. If 31–60°: 1. DF resection 2–4 mm. 2. Soft tissue releases as performed in less than 30°. 3. Elevate posterior capsule up to the linear aspera. 4. Elevate heads of gastrocnemius. 5. Dissection of the posterior capsule If greater than 60°: 1. DF resection 4 mm. 2. Soft tissue releases as in 31–60°. 3. Collateral ligament laxity may need to be accounted for with tightening or advancement. 1. Posteromedial capsular release and remnants of posterior cruciate ligament released. 2. Introduce a spacer to assess superficial medial MCL, release tight bands using number 11 blade in pie-crust manner. 3. Manipulate with repeated valgus stress whilst spacer is in place, until 2–3 mm of “springy give”, with greater accepted laxity in the lateral direction. 1. Posterior capsular release. 2. DF re-resection 1. Osteophyte removal and ligament balancing. 2. Medial capsular release in varus knees, followed by posterolateral capsular release if necessary. 3. DF re-resection
Berend 2006 Firestone 1992 Jain 2013
Meftah 2012
Mihalko 2003 Whiteside 2002
DF: distal femoral. PCL: posterior cruciate ligament. MCL: medial collateral ligament.
3.3.2.3. Soft tissue structures. The role of soft-tissue structures in the treatment of FFD is surprisingly poorly described, with only two relevant studies identified addressing this issue. Asano et al. assessed the role of soft-tissue tension on post-operative extension at one year post-operatively [32]. Using intraoperative customised tensometry Asano et al. found that increasing “soft tissue tension” of the knee in extension correlated with increasing FFD. “Soft tissue tension” was defined as the amount of axially applied distraction force required to open the extension gap to the thickness of the implant, although which soft tissue components (such as the posterior capsule or medial collateral ligament) specifically contributed to this phenomenon was not determined [32]. The importance of the extension gap in the prevention of post-operative flexion contracture has also been shown [27]. Using a specialised offset-type tension device, it was found that in varus knees, the medial extension gap was required to be at least one millimetre more than the flexion gap to avoid FFD (defined as five degrees short of extension) one-year post-operatively. Specifically, the risk of flexion contracture was 20%, eight percent and 0% when the medial extension gap was 0 mm, 0 to one millimetre and over one millimetre greater than the flexion gap. Okamoto's findings build on that of Asano, providing more specific insight as to tension into which soft-tissue structures may contribute to flexion contracture: in this case, his results suggest medial compartment tightness is required to be ameliorated to prevent FFD. Indeed, Okamoto postulates that leaving a residual four degrees of varus deformity would reduce the medial extension gap by one millimetre with a 70 mm wide tibia, and so surgeons in this scenario should account for this by using a thicker insert to maintain the recommended one millimetre excess extension gap to prevent FFD. 3.3.2.4. Other techniques and factors. A number of other intraoperative factors have been identified which may affect the development of FFD. Posterior condylar offset was been demonstrated to correlate with posterior tibial slope [28], and is theorised to increase tightness of the posterior soft-tissue structures, thereby limiting extension. However, the posterior condylar offset was not directly compared to post-operative extension, and therefore its role remains unverified. Additionally, the intraoperative measurement technique used during the TKA has been associated with post-operative range of motion. Computer-navigated TKA [21] and TKA performed with a minimally-invasive approach [25] both decrease the risk of post-operative FFD compared to conventional, TKA with intramedullary instruments. 3.3.3. Surgical algorithms Seven studies [5–11] reported the efficacy of intraoperative algorithms in correcting FFD. Whilst each study reported a slightly different surgical algorithm (see Table 2), the algorithms largely consisted of sequential osteophyte removal, followed by posterior soft-tissue releases, and in the case of remaining FFD, distal femoral re-cut. These operations all resulted in the correction of FFD to less than five degrees as measured by a goniometer at up to two years post-operatively, with the exception of three cases as reported by Whiteside and Mihalko due to tight hamstring muscles [11]. 4. Discussion The management of flexion contracture is crucial in preventing post-operative residual FFD, and maximising the positive outcomes of total knee arthroplasty. Although intraoperative measurement algorithms of flexion contracture have been well documented and associated with low post-operative incidence of FFD [5,7–11], their individual contributions and interactions remain unclear. This review has identified a set of predictors which affect the incidence of flexion contracture both immediately post-operatively and in the ensuing post-operative period (Figure 2). The findings are constrained by methodological limitations within the included studies which will be discussed in further detail below. Overall, pre-operative patient characteristics such as pre-operative FFD, and Please cite this article as: An VVG, et al, Factors affecting the incidence and management of fixed flexion deformity in total knee arthroplasty: A systematic review, Knee (2018), https://doi.org/10.1016/j.knee.2018.03.008
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intraoperative steps such as distal femoral resection, soft-tissue balancing and femoral component placement in flexion are key contributors to FFD correction. Due to the heterogeneity of studies, there remains insufficient data to adequately construct a predictive model at this point. Prolonged operative time is associated with increased complications and poorer outcome following TKA, specifically resulting in increased infection [12], blood loss and deep vein thrombosis [13]. A study of the New Zealand joint registry found that TKA operations lasting greater than 120 min were at elevated risk of subsequent revision [34]. Synthesising the identified steps into an integrated surgical model or algorithm to correct would streamline the decision-making process resulting in less surgical steps taken allowing for decreased operative time, leading to a lower complication rate. At this point, there remains insufficient data to create such a predictive model. This is due to a number of inherent errors conferred by study design, particularly measurement technique and follow-up duration. The majority of the identified studies measured range of motion using a clinical goniometer (Table 1). The reliability of the goniometer for range of motion is questionable [35], with discrepancies in goniometer-based measurements of up to five degrees. In the context of measuring FFD, where detectable differences in outcome can be seen at as little as five degrees, this degree of error would not be ideal for assessing whether a joint is restricted in range of motion or not. Three studies [26,27,30] included in this review also used radiographic measurements to determine post-operative extension range of motion. The reliability of radiographic measurements is not much better than that of the goniometer, with 95% confidence intervals of error between observers reported at up to 6.6° when measuring extension range of motion [36]. Computer navigation systems have demonstrated accuracy to within less than one degree, which would be more acceptable in the context of assessing FFD [37]. Future studies should employ computer navigation techniques to optimise the reliability of reported range of motion measurements. In addition to enhanced reliability, computer navigation measurements have been validated by several studies [38,39]. Notably, three studies included in this systematic review employed navigation measurements to assess end-extension range of motion, and therefore their results could be considered to be more reliable [22–24]. The timepoint at which extension was assessed post-operatively was highly variable, ranging from measurements taken intraoperatively to up to a mean follow-up of 70 months. This review found that only studies addressing distal femoral resection assessed range of motion intraoperatively to determine its effect [4,22,23,29]. Measurements taken months or years postoperatively may not accurately demonstrate the effect of intra-operative steps in correcting FFD, as FFD has been shown to change during the post-operative period [40,41]. In order to accurately assess the effect of surgical manoeuvres on FFD, future studies should collect “time zero” measurements (taken intraoperatively) of range of motion ideally with accurate measurement systems such as computer navigation, and ideally correlate these with future timepoints to assess how well these initial effects are maintained. Notably, studies in this review only addressed papers which investigated TKA employing the traditional mechanically aligned (MA) philosophy. MA TKA employs bony resections perpendicular to the mechanical axes of the femur and tibia [42]. On the other hand, kinematically aligned (KA) TKA is a novel philosophy which aims to recreate patient specific anatomy, in theory preserving native soft-tissue tension and kinematics [43]. The correction of FFD in KA TKA is yet to be assessed, and may lead research direction down a completely separate path. Early anecdotal experience with KA TKA in our institution has found that FFD can be corrected intraoperatively in the majority of patients with minimal additional bony resection and soft tissue releases, suggesting that a paradigm shift in the approach to FFD may be warranted. However, this has yet to be formally quantified and research into the KA approach to FFD is warranted. 5. Conclusion Our systematic review has identified a variety of pre-operative, and intraoperative steps which influence the incidence and correction of fixed-flexion deformity in total knee arthroplasty. At present, a predictive model could not be formed from the data available, due to methodological inconsistencies in the included studies as well as heterogeneous follow-up durations in the literature. The primary pre-operative factor predictive of post-operative fixed flexion deformity is pre-operative fixed flexion deformity. The intraoperative steps that have been described to correct fixed flexion deformity are: distal femoral resection, soft tissue release (of the medial and posterior compartments), sagittal placement of the femoral component, and posterior condylar offset, which affects posterior tibial slope. These factors are likely to interact, and therefore further investigation in an integrated model is crucial to developing a statistically sound and reliable intraoperative algorithm for surgeons to follow when correcting fixed flexion deformity. Future studies should measure range of motion immediately intraoperatively, with standardised, reliable measurement methods such as computer navigation. Acknowledgements The authors wish to acknowledges the support of the Sydney Orthopaedic Research Institute to perform this work. The authors also wish to acknowledge the assistance of Professor Michael Solomon and Dr David Parker. References [1] Tew M, Forster IW. Effect of knee replacement on flexion deformity. J Bone Joint Surg Br 1987;69:395–9. [2] Waters RL, Mulroy S. The energy expenditure of normal and pathologic gait. Gait Posture 1999;9:207–31.
Please cite this article as: An VVG, et al, Factors affecting the incidence and management of fixed flexion deformity in total knee arthroplasty: A systematic review, Knee (2018), https://doi.org/10.1016/j.knee.2018.03.008
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Curr Orthop Pract 2013;24: 659–64. [9] Meftah M, Blum YC, Raja D, Ranawat AS, Ranawat CS. Correcting fixed varus deformity with flexion contracture during total knee arthroplasty: the ‘inside-out’ technique: AAOS exhibit selection. J Bone Joint Surg Am 2012;94:e66. [10] Mihalko WM, Whiteside LA. Bone resection and ligament treatment for flexion contracture in knee arthroplasty. Clin Orthop Relat Res 2003:141–7. [11] Whiteside LA, Mihalko WM. Surgical procedure for flexion contracture and recurvatum in total knee arthroplasty. Clin Orthop Relat Res 2002:189–95. [12] Peersman G, Laskin R, Davis J, Peterson MG, Richart T. Prolonged operative time correlates with increased infection rate after total knee arthroplasty. HSS J 2006; 2:70–2. [13] Kang J, Jiang X, Wu B. Analysis of risk factors for lower-limb deep venous thrombosis in old patients after knee arthroplasty. Chin Med J (Engl) 2015;128:1358–62. [14] Royston P, Moons KG, Altman DG, Vergouwe Y. 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Incidence, predictors, and effects of residual flexion contracture on clinical outcomes of total knee arthroplasty. J Arthroplasty 2013;28:585–90. [20] Schurman DJ, Parker JN, Ornstein D. Total condylar knee replacement. A study of factors influencing range of motion as late as two years after arthroplasty. J Bone Joint Surg Am 1985;67:1006–14. [21] Bin Abd Razak HR, Yeo Jin S, Chong Chi H. Computer navigation results in less severe flexion contracture following total knee arthroplasty. J Arthroplasty 2014;29: 2369–72. [22] Cross MB, Nam D, Plaskos C, Sherman SL, Lyman S, Pearle AD, et al. Recutting the distal femur to increase maximal knee extension during TKA causes coronal plane laxity in mid-flexion. Knee 2012;19:875–9. [23] Liu DW, Reidy JF, Beller EM. The effect of distal femoral resection on fixed flexion deformity in total knee arthroplasty. J Arthroplasty 2016;31:98–102. [24] Lustig S, Scholes CJ, Stegeman TJ, Oussedik S, Coolican MRJ, Parker DA. Sagittal placement of the femoral component in total knee arthroplasty predicts knee flexion contracture at one-year follow-up. Int Orthop 2012;36:1835–9. [25] McAllister CM, Stepanian JD. The impact of minimally invasive surgical techniques on early range of motion after primary total knee arthroplasty. J Arthroplasty 2008;23:10–8. [26] Nagai K, Muratsu H, Matsumoto T, Takahara S, Kuroda R, Kurosaka M. Influence of intraoperative soft tissue balance on postoperative active knee extension in posterior-stabilized total knee arthroplasty. J Arthroplasty 2015;30:1155–9. [27] Okamoto S, Okazaki K, Mitsuyasu H, Matsuda S, Mizu-Uchi H, Hamai S, et al. Extension gap needs more than 1-mm laxity after implantation to avoid postoperative flexion contracture in total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc 2014;22:3174–80. [28] Onodera T, Majima T, Nishiike O, Kasahara Y, Takahashi D. Posterior femoral condylar offset after total knee replacement in the risk of knee flexion contracture. J Arthroplasty 2013;28:1112–6. [29] Smith CK, Chen JA, Howell SM, Hull ML. An in vivo study of the effect of distal femoral resection on passive knee extension. J Arthroplasty 2010;25:1137–42. [30] Zhang HM, Sun G, Zhao TJ, Gu LJ, Chen WH, Yin T, et al. Effect of femoral component flexion in total knee arthroplasty: one-year follow-up results. J Clin Rehabil Tissue Eng Res 2008;12:1771–4. [31] Gatha NM, Clarke HD, Fuchs R, Scuderi GR, Insall JN. Factors affecting postoperative range of motion after total knee arthroplasty. J Knee Surg 2004;17:196–202. [32] Asano H, Muneta T, Sekiya I. Soft tissue tension in extension in total knee arthroplasty affects postoperative knee extension and stability. Knee Surg Sports Traumatol Arthrosc 2008;16:999–1003. [33] Chaudhary R, Beaupre LA, Johnston DW. Knee range of motion during the first two years after use of posterior cruciate-stabilizing or posterior cruciate-retaining total knee prostheses. A randomized clinical trial. J Bone Joint Surg Am 2008;90:2579–86. [34] Young SW, Mutu-Grigg J, Frampton CM, Cullen J. Does speed matter? Revision rates and functional outcomes in TKA in relation to duration of surgery. J Arthroplasty 2014;29:1473–1477.e1. [35] Lenssen AF, van Dam EM, Crijns YH, Verhey M, Geesink RJ, van den Brandt PA, et al. Reproducibility of goniometric measurement of the knee in the in-hospital phase following total knee arthroplasty. BMC Musculoskelet Disord 2007;8:83. [36] Phillips A, Goubran A, Naim S, Searle D, Mandalia V, Toms A. Reliability of radiographic measurements of knee motion following knee arthroplasty for use in a virtual knee clinic. Ann R Coll Surg Engl 2012;94:506–12. [37] Lustig S, Fleury C, Goy D, Neyret P, Donell ST. The accuracy of acquisition of an imageless computer-assisted system and its implication for knee arthroplasty. Knee 2011;18:15–20. [38] Pitto RP, Graydon AJ, Bradley L, Malak SF, Walker CG, Anderson IA. Accuracy of a computer-assisted navigation system for total knee replacement. J Bone Joint Surg Br 2006;88(5):601. [39] Martelli S, Zaffagnini S, Bignozzi S, Lopomo N, Marcacci M. Description and validation of a navigation system for intra-operative evaluation of knee laxity. Comput Aided Surg 2007;12:181–8. [40] Quah C, Swamy G, Lewis J, Kendrew J, Badhe N. Fixed flexion deformity following total knee arthroplasty. A prospective study of the natural history. Knee 2012; 19:519–21. [41] Tanzer M, Miller J. The natural history of flexion contracture in total knee arthroplasty. A prospective study. Clin Orthop Relat Res 1989:129–34. [42] Luo CF. Reference axes for reconstruction of the knee. Knee 2004;11:251–7. [43] Schiraldi M, Bonzanini G, Chirillo D, de Tullio V. Mechanical and kinematic alignment in total knee arthroplasty. Ann Transl Med 2016;4:130.
Please cite this article as: An VVG, et al, Factors affecting the incidence and management of fixed flexion deformity in total knee arthroplasty: A systematic review, Knee (2018), https://doi.org/10.1016/j.knee.2018.03.008
Contents lists available at ScienceDirect
The Knee
Review
Factors affecting the incidence and management of fixed flexion deformity in total knee arthroplasty: A systematic review Vincent V.G. An a,b,⁎, Corey J. Scholes a, Brett A. Fritsch a,c a b c
Sydney Orthopaedic Research Institute, Chatswood, NSW 2067, Australia Sydney Medical School, University of Sydney, Camperdown, NSW 2050, Australia Department of Orthopaedics, Royal Prince Alfred Hospital, Camperdown, NSW, Australia
a r t i c l e
i n f o
Article history: Received 1 December 2017 Received in revised form 11 December 2017 Accepted 11 March 2018 Available online xxxx Keywords: Knee Arthroplasty Fixed flexion deformity Systematic review
a b s t r a c t Purpose: This study aimed to systematically review the literature and identify factors which would contribute to the intraoperative correction of FFD to frame a potential surgical algorithm or predictive model to guide intraoperative decision-making. Methods: Electronic searches of six databases were undertaken in April 2016 according to the PRISMA guidelines, and the reference lists of studies searched. Quality of studies was assessed using the STROBE checklist, and the Downs and Black Scores. Results: Twenty-five studies investigating 10, 679 knees were found to satisfy the inclusion and exclusion criteria. These studies described a variety of pre-operative and intra-operative factors which contribute to the development or correction of post-operative FFD. The only patient predictor of post-operative FFD was pre-operative FFD. The intra-operative steps described to correct FFD were: distal femoral resection, soft-tissue balancing (in the posterior and medial compartments), sagittal component flexion and posterior condylar offset. However, no studies investigated these in an integrated model. Conclusion: This review has identified various pre-, intra- and post-operative factors predictive of post-operative FFD. In practice, these factors are likely to interact, and therefore further investigation in an integrated model is crucial to developing a statistically sound and reliable intraoperative algorithm for surgeons to follow when correcting fixed flexion deformity. © 2018 Elsevier B.V. All rights reserved.
Contents 1. 2.
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Introduction . . . . . . . . . . . . . . . . . Methods . . . . . . . . . . . . . . . . . . . 2.1. Literature search . . . . . . . . . . . . 2.2. Selection criteria . . . . . . . . . . . . 2.3. Quality appraisal . . . . . . . . . . . . 2.4. Data extraction . . . . . . . . . . . . 2.5. Data analysis . . . . . . . . . . . . . Results . . . . . . . . . . . . . . . . . . . 3.1. Search results . . . . . . . . . . . . . 3.1.1. Article methodology and designs
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⁎ Corresponding author at: Sydney Orthopaedic Research Institute, Level 1, The Gallery, 445 Victoria Ave, Chatswood, NSW 2067, Australia. E-mail address: [email protected] (V.V.G. An).
https://doi.org/10.1016/j.knee.2018.03.008 0968-0160/© 2018 Elsevier B.V. All rights reserved.
Please cite this article as: An VVG, et al, Factors affecting the incidence and management of fixed flexion deformity in total knee arthroplasty: A systematic review, Knee (2018), https://doi.org/10.1016/j.knee.2018.03.008
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Quality of studies . . . . . . Findings of studies . . . . . 3.3.1. Patient factors . . . 3.3.2. Single operative steps 3.3.3. Surgical algorithms . 4. Discussion . . . . . . . . . . . . . 5. Conclusion . . . . . . . . . . . . Acknowledgements . . . . . . . . . . . References . . . . . . . . . . . . . . .
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1. Introduction In traditional mechanically aligned (MA) total knee arthroplasty (TKA), a key objective is to restore the mechanical axis (MA) of the knee in extension in both coronal and sagittal planes. A maximally extended knee that remains in considerable flexion (fixed flexion deformity or FFD) is observed in up to 17% of knees following TKA [1]. Post-operative FFD is associated with abnormal gait requiring excessive energy expenditure and quadriceps loading [2], with an increased risk of anterior knee pain, reduced function and a reduction in patient reported outcome scores [3]. Post-operative extension has been correlated with intraoperative range of motion [4], therefore the intraoperative correction of FFD in TKA is a key surgical outcome. Historically, FFD has been managed in an empirical manner via surgical algorithms which revolve around ligament balancing, releases and further distal resection if necessary. For example, Bellemans et al. proposed a four-step algorithm comprising osteophyte removal and ligament balancing, followed by transverse posterior capsular release, then distal femoral over-resection and finally tenotomy of the knee flexors [5], progressing to each successive step only if FFD was remaining. Although the success of published surgical algorithms is well-described [5–11], they involve a subsequent re-resection of the distal femur, which prolongs operative duration whilst resetting the cutting guides, increasing the risk of excessive bleeding, infection [12] and deep vein thrombosis [13]. Femoral recuts can be difficult to make accurately with all systems, and they result in a change in the joint line. The combination of a delayed surgical work flow, and concerns around accuracy, makes it desirable to be able to predict the distal femoral resection to achieve full extension in all deformities, prior to making the first femoral cut. A predictive model able to dictate the appropriate surgical steps to be undertaken to correct FFD in any given patient with the least number of operative steps would aid the pre-operative surgical planning process, leading to streamlined intraoperative decision making and reduced operative time. To develop such a model, a detailed understanding of all the factors involved in the development and intraoperative prevention of post-TKR FFD is required. The pre-operative characteristics which predispose patients to developing post-operative FFD should be identified and the contribution of each individual operative step to correcting FFD needs to be quantified. Once determined, these factors can be subject to multivariate regression analysis to develop an accurate and validated predictive model for achieving full extension [14]. This data-driven approach is a considerable departure from the previous empirical approach to FFD correction. The purpose of this systematic review was to identify those factors predisposing patients to post-operative FFD, as well as factors involved in the intraoperative correction of FFD, with the intention of proposing a predictive model to guide intraoperative decision-making. 2. Methods 2.1. Literature search This review was registered on the PROSPERO database (CRD42016037207). A systematic review of the literature was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [15]. Electronic searches were performed in the Ovid MEDLINE, PubMed, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, ACP Journal Club, and Database of Abstracts of Review of Effectiveness during April 2016. To achieve maximum sensitivity, the terms (“flexion contracture” OR “flexion deformity”) AND (“knee arthroplasty” OR “knee replacement”) were combined as keywords. The reference lists of retrieved articles were reviewed to identify any additional relevant studies as per the inclusion and exclusion criteria as listed below. 2.2. Selection criteria Studies eligible for this systematic review included English-language studies published at any time that addressed or reported pre-operative or intra-operative factors in total knee arthroplasty for osteoarthritis that affect post-operative fixed flexion deformity. Specifically, studies investigating pre-operative and intra-operative factors were included. Studies investigating rheumatoid arthritis or haemophiliac arthropathy were excluded. Case reports, abstracts and conference proceedings were also excluded. Please cite this article as: An VVG, et al, Factors affecting the incidence and management of fixed flexion deformity in total knee arthroplasty: A systematic review, Knee (2018), https://doi.org/10.1016/j.knee.2018.03.008
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2.3. Quality appraisal The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) was used to evaluate the structure, quality and reporting of studies [16]. Study design was classified using the NHMRC level of evidence grading. Further to this, the studies were appraised using the Downs and Black score [17]. 2.4. Data extraction Data regarding factors or strategies affecting the development or prevention of post-TKR FFD were extracted from the text, figures and tables of included references. The effect of each predictor on FFD post-TKR at any time-point was recorded. 2.5. Data analysis Due to heterogeneity in study designs and reporting methods, meta-analysis of outcomes could not be performed. The included studies were divided into three main categories based on the factors investigated: pre-operative factors, surgical steps and surgical algorithms. Pre-operative factors were variables that were associated with patients developing post-operative TKR. Surgical steps were individual measures employed intraoperatively to correct FFD and prevent the incidence of post-operative FFD. Studies investigating surgical algorithms assessed the success of sequences involving particular intraoperative steps employed to correct and prevent post-operative FFD. FFD as an endpoint was defined as deficit in extension range of motion measured at any time during the intra- or post-operative period. 3. Results 3.1. Search results The initial search yielded 433 articles. Title and abstract screening left 55 articles for full-text review. After applying the inclusion and exclusion criteria, 21 studies [3,5–11,18–30] were retained for further analysis. After searching the reference lists of the included articles a further four references [4, 31–33] were acquired for inclusion, leaving a total of 25 studies for further analysis (Figure 1). 3.1.1. Article methodology and designs Included studies employed a variety of designs, measurement techniques for extension range of motion and length of followup (Table 1). The literature search retrieved one randomised controlled trial, 20 cohort studies, three case–control studies and one cadaveric study. Knee range of motion was assessed at various time-points from immediately intraoperatively to beyond 72 months. Goniometers were used in 16 studies: two studies used computer navigation, three used radiographs, one study used intraoperative photographs and skin markers, whilst three did not report their method of assessment. Time of assessment ranged from measurements taken intraoperatively to measurements taken at a mean of 70 months, with a maximum of 120 months' follow-up (see Table 1). 3.2. Quality of studies The quality of included studies was determined by their NHMRC level of evidence. Only one study was level II, whilst 10 were level III studies, and 14 were level IV studies. The median Downs and Black score was 17 out of a possible 26 points (Range: 14–22). The components of the Downs and Black score most poorly satisfied were related to: – Item 12: were the participants representative of the entire population? – Item 15: was an attempt made to blind the measurement of the outcome? – Item 23: were study subjects randomised to intervention groups? – Item 24: was the randomised intervention concealed from patients and healthcare until recruitment was complete and irrevocable? 3.3. Findings of studies The included studies investigated a total of 10,679 knees. Papers investigated a variety of pre-operative factors, isolated intraoperative steps and the success of described surgical algorithms in correcting FFD. The identified factors are displayed by time in Figure 2. 3.3.1. Patient factors Five of the included studies [3,18–20,24] correlated pre-operative patient factors with the incidence of post-operative fixed flexion deformity. The factors predictive of post-operative FFD were male sex, increased age, and pre-operative FFD. The role of sex and age in the development of post-operative FFD is unclear. Goudie et al. directly compared the demographics of patients with less than five degree post-operative FFD and those with greater than five degree FFD at a mean of two years post-operatively and found that the proportion of males and mean age were significantly greater in patients with the N 5 degree FFD group (p = 0.01, p = 0.02) [18]. Please cite this article as: An VVG, et al, Factors affecting the incidence and management of fixed flexion deformity in total knee arthroplasty: A systematic review, Knee (2018), https://doi.org/10.1016/j.knee.2018.03.008
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Figure 1. PRISMA flow chart demonstrating the article search and retrieval process.
A later study by Lustig et al. contradicted this notion, finding no significant difference between patients with and without at least five degree FFD at the one-year post-operative mark in terms of gender or age [24]. On the other hand, the role of pre-operative FFD in the development of post-operative FFD is unanimous. Goudie et al. compared patients with and without post-operative FFD and found that the degree of pre-operative FFD was significantly greater in the group with post-operative FFD at 24 months [18]. Furthermore, Koh et al. via multivariable analysis found that every five degrees of preoperative FFD conferred a 1.7 times risk of post-operative FFD at an average of 35 months of follow-up, whilst Ritter et al. found that at a minimum of 72 months of follow-up, having a pre-operative FFD of between 20 and 50° conferred a 5.8 times risk of developing post-operative FFD, and one of five to 19° conferred a 2.9 times risk [3,19].
3.3.2. Single operative steps For those patients presenting with an FFD, included studies also investigated the effect of individual operative steps on FFD. In particular, the role of distal femoral resection, femoral component flexion, and soft-tissue balancing was investigated.
3.3.2.1. Distal femoral resection. Distal femoral resection has been examined by four separate groups [4,22,23,29], showing that greater resection of the distal femur restores a greater degree of extension. Using cadavers, Cross et al. investigated the effect of sequential two millimetre resections of the distal femur in excess of the thickness of the femoral implant (nine millimetres) on extension intraoperatively, and found that the first two millimetre resection brought the mean maximum extension from 9.7° of flexion to 6.4°, and a further two millimetres brought the mean Please cite this article as: An VVG, et al, Factors affecting the incidence and management of fixed flexion deformity in total knee arthroplasty: A systematic review, Knee (2018), https://doi.org/10.1016/j.knee.2018.03.008
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Table 1 Details of the study design, measurement techniques employed, follow-up period and Downs and Black score of the included studies. Author
Year
Design
Measurement technique
Time of post-op measurement
Downs and Black score
Bellemans Berend Firestone Jain Meftah Mihalko Whiteside Goudie Koh Lustig Ritter Schurman Bin Abd Razak Cross McAllister Nagai Okamoto Onodera Smith Zhang Bengs Gatha Chaudhary Liu Asano
2006 2006 1992 2013 2012 2003 2002 2011 2013 2012 2007 1985 2014 2012 2008 2015 2014 2013 2010 2008 2006 2004 2008 2016 2008
Cohort Cohort Cohort Cohort Cohort Cohort Cohort Case control Case control Case control Cohort Cohort Cohort Cadaver Cohort Cohort Cohort Cohort Cohort Cohort Cohort Cohort RCT Cohort Cohort
Goniometer Goniometer Goniometer Goniometer NR NR Goniometer Goniometer Goniometer Goniometer Goniometer Goniometer Goniometer Praxim Navigation Goniometer Radiographs Radiographs NR Photographs with skin markers Radiographs Goniometer Goniometer Goniometer Navigation Goniometer
24 months 38 months (1.6–77 months) 53 months (26–84 months) 12 months 3.1 years (1.7–4.9 years) 70 months (12–120 months) 24 months 24 months 35 months (24–72 months) 12 months At least 72 months 24 months 24 months Intraoperative 12 months 4 weeks 12 months NR Intraoperative 12 months Intraoperative 51 months (24–72 months) 24 months Intraoperative 12 months
18 17 15 14 16 16 17 17 18 18 17 15 17 22 20 19 20 16 20 15 21 16 22 21 14
FFD to 1.4° [22]. They proposed the “2 by 4” rule, which approximates that for every two millimetres of distal femoral resection, four degrees of FFD is corrected. Bengs and Scott, Smith et al. and Liu et al. used different approaches to assess the effect of distal femoral resection on extension [4,23,29]. Using augments with increasing thickness to mimic the effect of “excess” distal femur on FFD intraoperatively, Smith et al. found that for every two millimetres of bone resected, approximately 3.6° of extension was restored, whilst Liu et al. found that with the first two millimetres of distal femoral (DF) resection, 3.36° was restored. Both studies were in agreeance with Cross et al.'s findings. Meanwhile, Bengs et al. found that for every two millimetres of bone resected, nine degrees of passive extension could be restored. 3.3.2.2. Femoral component sagittal placement. The literature on the effect of the sagittal placement of the femoral component is sparse, with only two studies [24,30] having investigated the role of femoral component flexion on post-operative FFD at 12 months. Zhang et al. found that TKAs with femoral component flexion had a decreased extension range of motion at 12 months compared to those without, although it was not reported what constituted a femoral component being in flexion [30]. Furthermore, the method of measuring the range of motion was not reported. Lustig et al. subsequently investigated this relationship, and found that knees with greater than 3.5° of component flexion (as assessed by computer navigation) had a greater proportion of one year post-operative FFD (greater than five degrees) compared to those without component flexion [24].
Figure 2. Factors which affect fixed flexion deformity intraoperatively and during post-operative recovery.
Please cite this article as: An VVG, et al, Factors affecting the incidence and management of fixed flexion deformity in total knee arthroplasty: A systematic review, Knee (2018), https://doi.org/10.1016/j.knee.2018.03.008
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Table 2 Description of studies using algorithms to correct fixed flexion deformity, and the steps taken to correct this deformity. Author and year
Steps in algorithm
Bellemans 2006
1. Coronal balancing with osteophytes and 2 mm DF resection. 2. Posterior capsular and gastrocnemius release. 3. DF resection up to 4 mm. 4. Hamstring tenotomy 1. Osteophyte removal, 2. DF resection, 3. PCL release, 4. DF re-resection to 4 mm, soft tissue releases. 1. Osteophyte and loose body removal. 2. Additional DF resection. 3. Soft tissue release in extension and flexion (posteromedial in varus knees, and posterolateral in valgus knees) If less than 30°: 1. Osteophyte removal. 2. Posterior capsular release. 3. Release of collateral ligaments. 4. 2 mm DF re-resection. If 31–60°: 1. DF resection 2–4 mm. 2. Soft tissue releases as performed in less than 30°. 3. Elevate posterior capsule up to the linear aspera. 4. Elevate heads of gastrocnemius. 5. Dissection of the posterior capsule If greater than 60°: 1. DF resection 4 mm. 2. Soft tissue releases as in 31–60°. 3. Collateral ligament laxity may need to be accounted for with tightening or advancement. 1. Posteromedial capsular release and remnants of posterior cruciate ligament released. 2. Introduce a spacer to assess superficial medial MCL, release tight bands using number 11 blade in pie-crust manner. 3. Manipulate with repeated valgus stress whilst spacer is in place, until 2–3 mm of “springy give”, with greater accepted laxity in the lateral direction. 1. Posterior capsular release. 2. DF re-resection 1. Osteophyte removal and ligament balancing. 2. Medial capsular release in varus knees, followed by posterolateral capsular release if necessary. 3. DF re-resection
Berend 2006 Firestone 1992 Jain 2013
Meftah 2012
Mihalko 2003 Whiteside 2002
DF: distal femoral. PCL: posterior cruciate ligament. MCL: medial collateral ligament.
3.3.2.3. Soft tissue structures. The role of soft-tissue structures in the treatment of FFD is surprisingly poorly described, with only two relevant studies identified addressing this issue. Asano et al. assessed the role of soft-tissue tension on post-operative extension at one year post-operatively [32]. Using intraoperative customised tensometry Asano et al. found that increasing “soft tissue tension” of the knee in extension correlated with increasing FFD. “Soft tissue tension” was defined as the amount of axially applied distraction force required to open the extension gap to the thickness of the implant, although which soft tissue components (such as the posterior capsule or medial collateral ligament) specifically contributed to this phenomenon was not determined [32]. The importance of the extension gap in the prevention of post-operative flexion contracture has also been shown [27]. Using a specialised offset-type tension device, it was found that in varus knees, the medial extension gap was required to be at least one millimetre more than the flexion gap to avoid FFD (defined as five degrees short of extension) one-year post-operatively. Specifically, the risk of flexion contracture was 20%, eight percent and 0% when the medial extension gap was 0 mm, 0 to one millimetre and over one millimetre greater than the flexion gap. Okamoto's findings build on that of Asano, providing more specific insight as to tension into which soft-tissue structures may contribute to flexion contracture: in this case, his results suggest medial compartment tightness is required to be ameliorated to prevent FFD. Indeed, Okamoto postulates that leaving a residual four degrees of varus deformity would reduce the medial extension gap by one millimetre with a 70 mm wide tibia, and so surgeons in this scenario should account for this by using a thicker insert to maintain the recommended one millimetre excess extension gap to prevent FFD. 3.3.2.4. Other techniques and factors. A number of other intraoperative factors have been identified which may affect the development of FFD. Posterior condylar offset was been demonstrated to correlate with posterior tibial slope [28], and is theorised to increase tightness of the posterior soft-tissue structures, thereby limiting extension. However, the posterior condylar offset was not directly compared to post-operative extension, and therefore its role remains unverified. Additionally, the intraoperative measurement technique used during the TKA has been associated with post-operative range of motion. Computer-navigated TKA [21] and TKA performed with a minimally-invasive approach [25] both decrease the risk of post-operative FFD compared to conventional, TKA with intramedullary instruments. 3.3.3. Surgical algorithms Seven studies [5–11] reported the efficacy of intraoperative algorithms in correcting FFD. Whilst each study reported a slightly different surgical algorithm (see Table 2), the algorithms largely consisted of sequential osteophyte removal, followed by posterior soft-tissue releases, and in the case of remaining FFD, distal femoral re-cut. These operations all resulted in the correction of FFD to less than five degrees as measured by a goniometer at up to two years post-operatively, with the exception of three cases as reported by Whiteside and Mihalko due to tight hamstring muscles [11]. 4. Discussion The management of flexion contracture is crucial in preventing post-operative residual FFD, and maximising the positive outcomes of total knee arthroplasty. Although intraoperative measurement algorithms of flexion contracture have been well documented and associated with low post-operative incidence of FFD [5,7–11], their individual contributions and interactions remain unclear. This review has identified a set of predictors which affect the incidence of flexion contracture both immediately post-operatively and in the ensuing post-operative period (Figure 2). The findings are constrained by methodological limitations within the included studies which will be discussed in further detail below. Overall, pre-operative patient characteristics such as pre-operative FFD, and Please cite this article as: An VVG, et al, Factors affecting the incidence and management of fixed flexion deformity in total knee arthroplasty: A systematic review, Knee (2018), https://doi.org/10.1016/j.knee.2018.03.008
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intraoperative steps such as distal femoral resection, soft-tissue balancing and femoral component placement in flexion are key contributors to FFD correction. Due to the heterogeneity of studies, there remains insufficient data to adequately construct a predictive model at this point. Prolonged operative time is associated with increased complications and poorer outcome following TKA, specifically resulting in increased infection [12], blood loss and deep vein thrombosis [13]. A study of the New Zealand joint registry found that TKA operations lasting greater than 120 min were at elevated risk of subsequent revision [34]. Synthesising the identified steps into an integrated surgical model or algorithm to correct would streamline the decision-making process resulting in less surgical steps taken allowing for decreased operative time, leading to a lower complication rate. At this point, there remains insufficient data to create such a predictive model. This is due to a number of inherent errors conferred by study design, particularly measurement technique and follow-up duration. The majority of the identified studies measured range of motion using a clinical goniometer (Table 1). The reliability of the goniometer for range of motion is questionable [35], with discrepancies in goniometer-based measurements of up to five degrees. In the context of measuring FFD, where detectable differences in outcome can be seen at as little as five degrees, this degree of error would not be ideal for assessing whether a joint is restricted in range of motion or not. Three studies [26,27,30] included in this review also used radiographic measurements to determine post-operative extension range of motion. The reliability of radiographic measurements is not much better than that of the goniometer, with 95% confidence intervals of error between observers reported at up to 6.6° when measuring extension range of motion [36]. Computer navigation systems have demonstrated accuracy to within less than one degree, which would be more acceptable in the context of assessing FFD [37]. Future studies should employ computer navigation techniques to optimise the reliability of reported range of motion measurements. In addition to enhanced reliability, computer navigation measurements have been validated by several studies [38,39]. Notably, three studies included in this systematic review employed navigation measurements to assess end-extension range of motion, and therefore their results could be considered to be more reliable [22–24]. The timepoint at which extension was assessed post-operatively was highly variable, ranging from measurements taken intraoperatively to up to a mean follow-up of 70 months. This review found that only studies addressing distal femoral resection assessed range of motion intraoperatively to determine its effect [4,22,23,29]. Measurements taken months or years postoperatively may not accurately demonstrate the effect of intra-operative steps in correcting FFD, as FFD has been shown to change during the post-operative period [40,41]. In order to accurately assess the effect of surgical manoeuvres on FFD, future studies should collect “time zero” measurements (taken intraoperatively) of range of motion ideally with accurate measurement systems such as computer navigation, and ideally correlate these with future timepoints to assess how well these initial effects are maintained. Notably, studies in this review only addressed papers which investigated TKA employing the traditional mechanically aligned (MA) philosophy. MA TKA employs bony resections perpendicular to the mechanical axes of the femur and tibia [42]. On the other hand, kinematically aligned (KA) TKA is a novel philosophy which aims to recreate patient specific anatomy, in theory preserving native soft-tissue tension and kinematics [43]. The correction of FFD in KA TKA is yet to be assessed, and may lead research direction down a completely separate path. Early anecdotal experience with KA TKA in our institution has found that FFD can be corrected intraoperatively in the majority of patients with minimal additional bony resection and soft tissue releases, suggesting that a paradigm shift in the approach to FFD may be warranted. However, this has yet to be formally quantified and research into the KA approach to FFD is warranted. 5. Conclusion Our systematic review has identified a variety of pre-operative, and intraoperative steps which influence the incidence and correction of fixed-flexion deformity in total knee arthroplasty. At present, a predictive model could not be formed from the data available, due to methodological inconsistencies in the included studies as well as heterogeneous follow-up durations in the literature. The primary pre-operative factor predictive of post-operative fixed flexion deformity is pre-operative fixed flexion deformity. The intraoperative steps that have been described to correct fixed flexion deformity are: distal femoral resection, soft tissue release (of the medial and posterior compartments), sagittal placement of the femoral component, and posterior condylar offset, which affects posterior tibial slope. These factors are likely to interact, and therefore further investigation in an integrated model is crucial to developing a statistically sound and reliable intraoperative algorithm for surgeons to follow when correcting fixed flexion deformity. Future studies should measure range of motion immediately intraoperatively, with standardised, reliable measurement methods such as computer navigation. Acknowledgements The authors wish to acknowledges the support of the Sydney Orthopaedic Research Institute to perform this work. 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Please cite this article as: An VVG, et al, Factors affecting the incidence and management of fixed flexion deformity in total knee arthroplasty: A systematic review, Knee (2018), https://doi.org/10.1016/j.knee.2018.03.008
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Please cite this article as: An VVG, et al, Factors affecting the incidence and management of fixed flexion deformity in total knee arthroplasty: A systematic review, Knee (2018), https://doi.org/10.1016/j.knee.2018.03.008