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Cementing the femoral component in total knee arthroplasty: Which technique is the best?
The Knee 16 (2009) 265–268
Contents lists available at ScienceDirect
The Knee
Cementing the femoral component in total knee arthroplasty: Which technique is the best? Michaël Vaninbroukx a,⁎, Luc Labey b, Bernardo Innocenti b, Johan Bellemans a a b
Department of Orthopaedic Surgery, University Hospital Leuven, Weligerveld 1, 3212 Pellenberg, Belgium European Centre for Knee Research, Belgium
a r t i c l e
i n f o
Article history: Received 28 September 2008 Received in revised form 20 November 2008 Accepted 21 November 2008 Keywords: Cement penetration Femoral component TKA Cementing technique
a b s t r a c t Although several techniques exist for cementing the femoral component in TKA, no data are available on which is the best one to use. We therefore compared four cementing techniques in an anatomical open pore sawbone model (n = 20), in order to investigate the influence of cementation technique on overall cement penetration as well as length of the cement mantle over the different cuts. The technique which included cement application onto the anterior and distal bone surfaces, as well as the posterior flanges of the prosthesis, was statistically superior to the other techniques. We therefore advocate this technique as the standard for cementing the femoral component. © 2008 Elsevier B.V. All rights reserved.
1. Introduction
2. Materials and methods
Aseptic loosening of the femoral component (FC) in total knee arthroplasty (TKA) can be caused by many factors. Inadequate preparation of the bone surface, malalignment of the components, as well as cementing technique and component design are technical factors that can adversely affect component fixation and clinical success [1–7]. Although femoral component loosening is a relatively uncommon complication in TKA, the recent evolution towards the use of so called high performance TKA designs may allow the patient to perform more strenuous activities with his knee prosthesis in situ, and could therefore increase the risk for aseptic loosening [8]. Optimizing implant fixation remains a valid concern, where both implant design as well as cementing technique plays a significant role [9]. Some evidence exists already on the effect of cement mantle on prosthetic component fixation. Previous studies have shown that a cement penetration depth of 3 mm is optimal, since thicker cement layers (5–10 mm) increase the risk for thermal damage [10,11]. Using current cementation techniques and component designs it is unclear how cement penetration be obtained in a consistent manner for the femoral component in TKA. In this study we therefore compared four different cementing techniques in an anatomical open pore sawbone model using a contemporary TKA design and standard polymethylmethacrylate (PMMA) cement, in order to investigate the effect on overall cement penetration as well as length of the cement mantle over the different cuts.
The study was performed using a specifically developed open pore composite sawbone model (item nr 1130-130, Sawbones®, Malmo, Sweden), mimicking the open cell structure of the distal femoral cancellous bone. Twenty bone models were used for the tests, each identical in size and composition. The models consisted of an anatomic replica of the distal femur composed of a fiber filled epoxy cortex injected around an open pore polyurethane foam. This model has been validated previously with respect to the structural properties [12]. The cancellous cell structure was identical in all models (cell size 1.5 to 2.5 mm, open N95%). The sawbones (n = 20) were prepared for a size 5 FC of the Genesis II PS knee prosthesis® (Smith & Nephew, Memphis, TN, USA) with the standard cutting block size 5. The PMMA bone cement (Surgical Simplex P®, Howmedica) was stored and prepared in a controlled environment of 20 °C and 70% relative humidity. The cement was manually mixed following the instructions of the manufacturer and was applied after 4 min in a doughy state. Immediately before cement application an aluminium foil covered with vaseline was applied onto on the inner surface of the FC, in order to facilitate component removal for the analyses. The same amount of cement (37 g) was equally applied to the surfaces which were identical in all techniques (bone surface or inner surface of the component). Four cementing techniques were investigated, each in five sawbones (Fig. 1):
⁎ Corresponding author. Tel.: +32 16 33 88 27; fax: +32 16 33 88 24. E-mail address: [email protected] (M. Vaninbroukx). 0968-0160/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.knee.2008.11.015
1. In the first technique, 37 g of cement was divided in 25 g to cover the anterior and distal femoral cuts with a horseshoe shaped layer
266
M. Vaninbroukx et al. / The Knee 16 (2009) 265–268
Fig. 1. The four different cementing techniques.
and the rest was equally spread over the two posterior flanges of the component. The component was then placed and impacted onto the femur using the specific component holder supplied by the manufacturer. 2. In the second technique, 37 g of cement was applied evenly over the entire bone surface. No cement was applied to the implant. 3. In the third technique, 37 g of cement was applied uniformly on the FC only. No cement was applied on the bone. 4. In the fourth technique, 37 g of bone cement was divided in two equal parts. One half was used to cover the entire femoral bone surface and the other half was spread on the component. After impaction, manual pressure along the long axis of the femur was applied for 15 min to ensure contact between the FC and bone surface. In all cases, the excess of cement was removed using a curette and weighed. After total polymerisation of the cement – at 20 min – the component was removed by a gentle tap. The specimens were then cut in the sagittal plane exactly through the middle of the medial and lateral condyles using a band saw. For this purpose the model was fixed into a specially fabricated clamp to hold the condyles in the correct orientation and position during cutting in an effort to maximise reproducibility. A slow cutting speed was used in order to prevent damage to the surfaces. The cut surfaces were subsequently cleaned with pressured air to remove debris. Digital high resolution (600 dpi) pictures were taken of all sections together with a measuring scale using a Nikon D200 camera with a 105 mm — 1:2.8 G objective. The images were imported in CorelDRAW 9, together with the cross section of the Genesis II FC at the identical level as the cut. Both images were superimposed in order to identify the outer bone surface from where cement penetration was calculated. Therefore, any cement that was present between the inner surface of the component and the outer surface of the bone could be excluded from the analysis (since it should not be considered as having penetrated into the cancellous structure).
Fig. 2. Section through the lateral condyle, with superposition of the inner surface of the femoral component. A: Anterior cut; B: anterior chamfer; C: distal cut; D: posterior chamfer; E: posterior cut.
M. Vaninbroukx et al. / The Knee 16 (2009) 265–268
267
Finally, all composite pictures were imported in Corel PHOTOPAINT 9 to quantify cement penetration. This was done for five distinctive zones: the anterior cut, the anterior chamfer, the distal cut, the posterior chamfer and the posterior cut (Fig. 2). The cement layer in each of these zones was identified using the Magic Wand tool. This tool defines irregularly shaped selections that include all adjacent pixels that are similar in colour (defined by their hue) to the selected pixel. The hue tolerance was chosen to be 10. The number of pixels in the selection was used to calculate the area of the cement layer in the investigated zone, and the average penetration depth was calculated from this area by dividing it by the length of the cut for that zone. For the anterior and posterior cuts, the effective length of the cement layer was measured since the cement mantle did not necessarily span the whole length of the cut in these zones. Statistical analysis was performed using the unpaired 2-tailed Student's T-test. Two reproducibility tests were performed in order to quantify the precision of the whole procedure. In a first test, superimposing the femoral component cross section on the digital pictures was done independently and blinded by two operators. In a second test, selection of the cement mantle was done independently by another investigator using another image processing software (Image-Pro Plus). Values for the cement penetration depth were then compared among all operators.
Table 1 Cement penetration and length of the cement mantle for the three main zones in all four techniques
3. Results
Although technique 4 demonstrated the best cement penetration at the anterior and posterior surfaces (however not statistically significant), it also showed a statistically significant inferior result in length of the anterior cement mantle. Overall, technique 1 had the best results with respect to cement penetration and length of cement mantle. Technique 3 was clearly inferior to any of the other techniques.
The reproducibility studies that were performed showed that it was possible to evaluate penetration depth with the described procedure with a precision of better than 0.5 mm for all but one zone (the distal cut at the medial side), which showed an average intraoperator difference in penetration depth of 0.94 mm. The average penetration depth was not significantly different between the medial and lateral condyles for any of the five zones. There is no statistical difference in cement penetration of the anterior chamfer, distal cut and posterior chamfer between the four techniques. Therefore only the results for the distal cut will be displayed to compare with the anterior and posterior cuts. Fig. 3 shows an overview of the cement penetration depths in the three main zones (anterior, distal and posterior cut) for each technique. Overall, the cement layer had a thickness between 2 mm and 4 mm. Cement penetration was greatest on the distal surface, and was less on the anterior and posterior surfaces, regardless of cement technique. Technique 3 was significantly worse in penetration depth on the anterior and posterior surfaces compared to the three other techniques. Both the anterior and posterior cuts show less cement penetration with this technique and the result is less consistent. Technique 4 showed the best cement penetration at the anterior and distal cuts, although this was not statistically significant.
Technique Anterior cut
Distal cut
Posterior cut
Length (mm) Depth (mm) Depth (mm) Length (mm) Depth (mm) 1 2 3 4
31.5 (2.17) 32.4 (1.56) 9.8 (5.22) 23.5 (3.60)
2.6 (0.41) 2.7 (0.30) 2.0 (1.04) 3.0 (0.31)
3.7 (0.59) 3.7 (0.90) 3.7 (0.60) 4.1 (0.67)
16.9 (3.38) 16.9 (2.83) 9.1 (4.29) 18.4 (2.05)
3.4 (1.28) 2.5 (0.79) 2.0 (0.85) 3.2 (1.11)
The length of the cement mantle for the four techniques at the level of the anterior and posterior cuts is shown in Table 1. The length of the anterior cement mantle for technique 4 was significantly poorer compared to techniques 1 and 2. Technique 3 was significantly worse with respect to length of both the anterior and posterior cement mantles. The obtained p-values are listed in Table 2. No p-values are shown for the chamfers and the distal cut, because none of them showed any statistically significant difference. Statistically inferior results were noted for: • Technique 3 with respect to the length of the anterior and posterior cement mantles and regarding cement penetration in the posterior cut, • Technique 2 regarding cement penetration in the posterior cut, and • Technique 4 regarding the length of the anterior cement mantle.
4. Discussion In this study we have investigated the influence of cementing technique on cement penetration depth and length of cement mantle for the femoral component in TKA. Although previous studies on cementing the femoral component have never looked into the actual length of the cement mantle, we believe that this factor is important as well. A lesser length in cement mantle at the level of the anterior or posterior cut may jeopardize the
Table 2 p-values of the different zones compared in each technique
Length anterior cement mantle
Cement penetration anterior cut
Length posterior cement mantle
Cement penetration posterior cut
Fig. 3. Cement penetration depths and standard deviation for the three main zones (anterior, distal and posterior cuts) for all cementing techniques.
Technique
_Technique
p-value
1 1 1 2 2 3 1 1 1 2 2 3 1 1 1 2 2 3 1 1 1 2 2 3
2 3 4 3 4 4 2 3 4 3 4 4 2 3 4 3 4 4 2 3 4 3 4 4
0.154721189 4.89137E− 05 0.00604533 2.74185E− 05 0.001912148 0.002498 0.782116 0.230118 0.354362 0.193563 0.462451 0.126887 0.977392 0.001037 0.286833 0.000506 0.232377 3.1771E− 05 0.04134 0.003909 0.17323 0.138753 0.382162 0.033519
The numbers in bold show statistically significant differences (p b 0.05).
268
M. Vaninbroukx et al. / The Knee 16 (2009) 265–268
overall component fixation and may increase the likelihood for aseptic loosening. In our study we have demonstrated that the main differences among the investigated techniques can be noted at the level of the posterior cut and, to a lesser extent on the anterior cut. It is not so surprising that these anterior and posterior surfaces are the most critical in obtaining an adequate cement layer, because of the tight fit between the femoral prosthesis and the underlying bone, as well the tangential way the component is applied onto the resected anterior and posterior surfaces. King and Scott [2] have demonstrated the importance of cementing the posterior flange and noted premature aseptic loosening due to an inferior cementing technique at that level. In order to enhance cement penetration, Labutti et al. [1] have even suggested a technique with direct pressured cement injection at the posterior flanges. Previous studies have shown that a cement penetration depth of 3 mm is advisable and that thicker cement layers (5–10 mm) increase the risk for thermal damage [10,11]. In our study the average penetration depth of all techniques except the third was within this range. Based upon the results of our work, we conclude that technique 1, where cement was applied onto the anterior and distal bone surfaces, as well as the posterior flanges of the prosthesis, was statistically superior to the other techniques. A weakness of our study is that we did not standardize the force applied during impaction of the component nor the pressurization during the setting faze of the cement. All the cases however were subsequently performed by the same investigator (M. V.). Manual impaction of the FC was done in all cases until the inner surface of the component was in contact with the bone surface. This was controlled visually. To ensure contact until hardening of the cement, manual pressure was given for 15 min. Our study was performed using an artificial sawbone model. Sawbones were used for the sake of reproducibility, and as a result some variables which are clinically relevant are not evaluated in the study, including the effect of intramedullary bleeding and accurate surface preparation [3–6,13,14]. Previous studies have however proven the accuracy of these models in mimicking the structural properties of the natural situation, with significantly lower variability in testing compared to cadaveric specimens, and therefore offering a more reliable research model [12,15,16]. In view of this we therefore believe that our experimental set-up is valid and in view of the current technology available, probably the most appropriate for the specific question we wanted to investigate. 5. Conclusion In this study we investigated the effect of four different cementing techniques on overall cement penetration as well as length of the cement mantle. The technique which included cement application onto the anterior and distal bone surfaces, as well as the posterior
flanges of the prosthesis, was statistically superior to the other techniques. We therefore advocate this technique as the standard for cementing the femoral component in TKA. 6. Conflict of interest The first author Michael Vaninbroukx does not have any disclosure to make. Luc Labey and Bernardo Innocenti are both employees of the Smith & Nephew company. They are both working at the European Centre for Knee Research (Smith & Nephew) in Leuven, Belgium. The senior author, Johan Bellemans, is a consultant for the Smith & Nephew Company and supervises studies in the European Centre for Knee Research, Leuven, Belgium. Acknowledgment I would like to thank the Smith & Nephew company for providing all the necessary material for this study. References [1] Labutti RS, Bayers-Thering M, Krackow KA. Enhancing femoral cement fixation in total knee arthroplasty. J Arthroplasty Dec 2003;18(8):979–83. [2] King TV, Scott RD. Femoral component loosening in total knee arthroplasty. Clin Orthop Relat Res Apr 1985;194:285–90. [3] Majkowski RS, Miles AW, Bannister GC, Perkins J, Taylor GJ. Bone surface preparation in cemented joint replacement. J Bone Jt Surg, Br May 1993;75B(3):459–63. [4] Maistrelli GL, Antonelli L, Fornasier V, Mahomed N. Cement penetration with pulsed lavage versus syringe irrigation in total knee arthroplasty. Clin Orthop Relat Res Mar 1995;312:261–5. [5] Benjamin JB, Gie GA, Lee AJ, Ling RS, Volz RG. Cementing technique and the effects of bleeding. J Bone Jt Surg, Br Aug 1987;69B(4):620–4. [6] Norton MR, Eyres KS. Irrigation and suction technique to ensure reliable cement penetration for total knee arthroplasty. J Arthroplasty Jun 2000;15(4):468–74. [7] Dorr LD, Lindberg JP, Claude-Faugere M, Malluche HH. Factors influencing the intrusion of methylmethacrylate into human tibiae. Clin Orthop Relat Res Mar 1984;183:147–52. [8] Han HS, Kang SB, Yoon KS. High incidence of loosening of the femoral component in legacy posterior stabilised-flex total knee replacement. J Bone Jt Surg, Br Nov 2007;89B(11):1457–61. [9] Scuderi GR. Successful results with a high flexion posterior stabilised knee prosthesis. J Bone Jt Surg, Br Dec 21 2007 Electronic letter. [10] Huiskes R, Slooff TJ. Thermal injury of cancellous bone following pressured penetration of acrylic cement. Trans Orthop Res Soc Jun 1981;6:134. [11] Walker PS, Soudry M, Ewald FC, McVickar H. Control of cement penetration in total knee arthroplasty. Clin Orthop Relat Res 1984 May;185:155–64. [12] Heiner AD, Brown TD. Structural properties of a new design of composite replicate femurs and tibias. J Biomech Jun 2001;34(6):773–81. [13] Miller MA, Race A, Gupta S, Higham P, Clarke MT, Mann KA. The role of cement viscosity on cement–bone apposition and strength: an in vitro model with medullary bleeding. J Arthroplasty 2007 Jan;22(1):109–16. [14] Stannage K, Shakespeare D, Bulsara M. Suction technique to improve cement penetration under the tibial component in total knee arthroplasty. Knee Mar 2003;10:67–73. [15] Cristofolini L, Viceconti M. Mechanical validation of whole bone composite tibia models. J Biomech Mar 2000;33(3):279–88. [16] Cristofolini L, Viceconti M, Cappello A, Toni A. Mechanical validation of whole bone composite femur models. J Biomech Apr 1996;29(4):525–35.
Contents lists available at ScienceDirect
The Knee
Cementing the femoral component in total knee arthroplasty: Which technique is the best? Michaël Vaninbroukx a,⁎, Luc Labey b, Bernardo Innocenti b, Johan Bellemans a a b
Department of Orthopaedic Surgery, University Hospital Leuven, Weligerveld 1, 3212 Pellenberg, Belgium European Centre for Knee Research, Belgium
a r t i c l e
i n f o
Article history: Received 28 September 2008 Received in revised form 20 November 2008 Accepted 21 November 2008 Keywords: Cement penetration Femoral component TKA Cementing technique
a b s t r a c t Although several techniques exist for cementing the femoral component in TKA, no data are available on which is the best one to use. We therefore compared four cementing techniques in an anatomical open pore sawbone model (n = 20), in order to investigate the influence of cementation technique on overall cement penetration as well as length of the cement mantle over the different cuts. The technique which included cement application onto the anterior and distal bone surfaces, as well as the posterior flanges of the prosthesis, was statistically superior to the other techniques. We therefore advocate this technique as the standard for cementing the femoral component. © 2008 Elsevier B.V. All rights reserved.
1. Introduction
2. Materials and methods
Aseptic loosening of the femoral component (FC) in total knee arthroplasty (TKA) can be caused by many factors. Inadequate preparation of the bone surface, malalignment of the components, as well as cementing technique and component design are technical factors that can adversely affect component fixation and clinical success [1–7]. Although femoral component loosening is a relatively uncommon complication in TKA, the recent evolution towards the use of so called high performance TKA designs may allow the patient to perform more strenuous activities with his knee prosthesis in situ, and could therefore increase the risk for aseptic loosening [8]. Optimizing implant fixation remains a valid concern, where both implant design as well as cementing technique plays a significant role [9]. Some evidence exists already on the effect of cement mantle on prosthetic component fixation. Previous studies have shown that a cement penetration depth of 3 mm is optimal, since thicker cement layers (5–10 mm) increase the risk for thermal damage [10,11]. Using current cementation techniques and component designs it is unclear how cement penetration be obtained in a consistent manner for the femoral component in TKA. In this study we therefore compared four different cementing techniques in an anatomical open pore sawbone model using a contemporary TKA design and standard polymethylmethacrylate (PMMA) cement, in order to investigate the effect on overall cement penetration as well as length of the cement mantle over the different cuts.
The study was performed using a specifically developed open pore composite sawbone model (item nr 1130-130, Sawbones®, Malmo, Sweden), mimicking the open cell structure of the distal femoral cancellous bone. Twenty bone models were used for the tests, each identical in size and composition. The models consisted of an anatomic replica of the distal femur composed of a fiber filled epoxy cortex injected around an open pore polyurethane foam. This model has been validated previously with respect to the structural properties [12]. The cancellous cell structure was identical in all models (cell size 1.5 to 2.5 mm, open N95%). The sawbones (n = 20) were prepared for a size 5 FC of the Genesis II PS knee prosthesis® (Smith & Nephew, Memphis, TN, USA) with the standard cutting block size 5. The PMMA bone cement (Surgical Simplex P®, Howmedica) was stored and prepared in a controlled environment of 20 °C and 70% relative humidity. The cement was manually mixed following the instructions of the manufacturer and was applied after 4 min in a doughy state. Immediately before cement application an aluminium foil covered with vaseline was applied onto on the inner surface of the FC, in order to facilitate component removal for the analyses. The same amount of cement (37 g) was equally applied to the surfaces which were identical in all techniques (bone surface or inner surface of the component). Four cementing techniques were investigated, each in five sawbones (Fig. 1):
⁎ Corresponding author. Tel.: +32 16 33 88 27; fax: +32 16 33 88 24. E-mail address: [email protected] (M. Vaninbroukx). 0968-0160/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.knee.2008.11.015
1. In the first technique, 37 g of cement was divided in 25 g to cover the anterior and distal femoral cuts with a horseshoe shaped layer
266
M. Vaninbroukx et al. / The Knee 16 (2009) 265–268
Fig. 1. The four different cementing techniques.
and the rest was equally spread over the two posterior flanges of the component. The component was then placed and impacted onto the femur using the specific component holder supplied by the manufacturer. 2. In the second technique, 37 g of cement was applied evenly over the entire bone surface. No cement was applied to the implant. 3. In the third technique, 37 g of cement was applied uniformly on the FC only. No cement was applied on the bone. 4. In the fourth technique, 37 g of bone cement was divided in two equal parts. One half was used to cover the entire femoral bone surface and the other half was spread on the component. After impaction, manual pressure along the long axis of the femur was applied for 15 min to ensure contact between the FC and bone surface. In all cases, the excess of cement was removed using a curette and weighed. After total polymerisation of the cement – at 20 min – the component was removed by a gentle tap. The specimens were then cut in the sagittal plane exactly through the middle of the medial and lateral condyles using a band saw. For this purpose the model was fixed into a specially fabricated clamp to hold the condyles in the correct orientation and position during cutting in an effort to maximise reproducibility. A slow cutting speed was used in order to prevent damage to the surfaces. The cut surfaces were subsequently cleaned with pressured air to remove debris. Digital high resolution (600 dpi) pictures were taken of all sections together with a measuring scale using a Nikon D200 camera with a 105 mm — 1:2.8 G objective. The images were imported in CorelDRAW 9, together with the cross section of the Genesis II FC at the identical level as the cut. Both images were superimposed in order to identify the outer bone surface from where cement penetration was calculated. Therefore, any cement that was present between the inner surface of the component and the outer surface of the bone could be excluded from the analysis (since it should not be considered as having penetrated into the cancellous structure).
Fig. 2. Section through the lateral condyle, with superposition of the inner surface of the femoral component. A: Anterior cut; B: anterior chamfer; C: distal cut; D: posterior chamfer; E: posterior cut.
M. Vaninbroukx et al. / The Knee 16 (2009) 265–268
267
Finally, all composite pictures were imported in Corel PHOTOPAINT 9 to quantify cement penetration. This was done for five distinctive zones: the anterior cut, the anterior chamfer, the distal cut, the posterior chamfer and the posterior cut (Fig. 2). The cement layer in each of these zones was identified using the Magic Wand tool. This tool defines irregularly shaped selections that include all adjacent pixels that are similar in colour (defined by their hue) to the selected pixel. The hue tolerance was chosen to be 10. The number of pixels in the selection was used to calculate the area of the cement layer in the investigated zone, and the average penetration depth was calculated from this area by dividing it by the length of the cut for that zone. For the anterior and posterior cuts, the effective length of the cement layer was measured since the cement mantle did not necessarily span the whole length of the cut in these zones. Statistical analysis was performed using the unpaired 2-tailed Student's T-test. Two reproducibility tests were performed in order to quantify the precision of the whole procedure. In a first test, superimposing the femoral component cross section on the digital pictures was done independently and blinded by two operators. In a second test, selection of the cement mantle was done independently by another investigator using another image processing software (Image-Pro Plus). Values for the cement penetration depth were then compared among all operators.
Table 1 Cement penetration and length of the cement mantle for the three main zones in all four techniques
3. Results
Although technique 4 demonstrated the best cement penetration at the anterior and posterior surfaces (however not statistically significant), it also showed a statistically significant inferior result in length of the anterior cement mantle. Overall, technique 1 had the best results with respect to cement penetration and length of cement mantle. Technique 3 was clearly inferior to any of the other techniques.
The reproducibility studies that were performed showed that it was possible to evaluate penetration depth with the described procedure with a precision of better than 0.5 mm for all but one zone (the distal cut at the medial side), which showed an average intraoperator difference in penetration depth of 0.94 mm. The average penetration depth was not significantly different between the medial and lateral condyles for any of the five zones. There is no statistical difference in cement penetration of the anterior chamfer, distal cut and posterior chamfer between the four techniques. Therefore only the results for the distal cut will be displayed to compare with the anterior and posterior cuts. Fig. 3 shows an overview of the cement penetration depths in the three main zones (anterior, distal and posterior cut) for each technique. Overall, the cement layer had a thickness between 2 mm and 4 mm. Cement penetration was greatest on the distal surface, and was less on the anterior and posterior surfaces, regardless of cement technique. Technique 3 was significantly worse in penetration depth on the anterior and posterior surfaces compared to the three other techniques. Both the anterior and posterior cuts show less cement penetration with this technique and the result is less consistent. Technique 4 showed the best cement penetration at the anterior and distal cuts, although this was not statistically significant.
Technique Anterior cut
Distal cut
Posterior cut
Length (mm) Depth (mm) Depth (mm) Length (mm) Depth (mm) 1 2 3 4
31.5 (2.17) 32.4 (1.56) 9.8 (5.22) 23.5 (3.60)
2.6 (0.41) 2.7 (0.30) 2.0 (1.04) 3.0 (0.31)
3.7 (0.59) 3.7 (0.90) 3.7 (0.60) 4.1 (0.67)
16.9 (3.38) 16.9 (2.83) 9.1 (4.29) 18.4 (2.05)
3.4 (1.28) 2.5 (0.79) 2.0 (0.85) 3.2 (1.11)
The length of the cement mantle for the four techniques at the level of the anterior and posterior cuts is shown in Table 1. The length of the anterior cement mantle for technique 4 was significantly poorer compared to techniques 1 and 2. Technique 3 was significantly worse with respect to length of both the anterior and posterior cement mantles. The obtained p-values are listed in Table 2. No p-values are shown for the chamfers and the distal cut, because none of them showed any statistically significant difference. Statistically inferior results were noted for: • Technique 3 with respect to the length of the anterior and posterior cement mantles and regarding cement penetration in the posterior cut, • Technique 2 regarding cement penetration in the posterior cut, and • Technique 4 regarding the length of the anterior cement mantle.
4. Discussion In this study we have investigated the influence of cementing technique on cement penetration depth and length of cement mantle for the femoral component in TKA. Although previous studies on cementing the femoral component have never looked into the actual length of the cement mantle, we believe that this factor is important as well. A lesser length in cement mantle at the level of the anterior or posterior cut may jeopardize the
Table 2 p-values of the different zones compared in each technique
Length anterior cement mantle
Cement penetration anterior cut
Length posterior cement mantle
Cement penetration posterior cut
Fig. 3. Cement penetration depths and standard deviation for the three main zones (anterior, distal and posterior cuts) for all cementing techniques.
Technique
_Technique
p-value
1 1 1 2 2 3 1 1 1 2 2 3 1 1 1 2 2 3 1 1 1 2 2 3
2 3 4 3 4 4 2 3 4 3 4 4 2 3 4 3 4 4 2 3 4 3 4 4
0.154721189 4.89137E− 05 0.00604533 2.74185E− 05 0.001912148 0.002498 0.782116 0.230118 0.354362 0.193563 0.462451 0.126887 0.977392 0.001037 0.286833 0.000506 0.232377 3.1771E− 05 0.04134 0.003909 0.17323 0.138753 0.382162 0.033519
The numbers in bold show statistically significant differences (p b 0.05).
268
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overall component fixation and may increase the likelihood for aseptic loosening. In our study we have demonstrated that the main differences among the investigated techniques can be noted at the level of the posterior cut and, to a lesser extent on the anterior cut. It is not so surprising that these anterior and posterior surfaces are the most critical in obtaining an adequate cement layer, because of the tight fit between the femoral prosthesis and the underlying bone, as well the tangential way the component is applied onto the resected anterior and posterior surfaces. King and Scott [2] have demonstrated the importance of cementing the posterior flange and noted premature aseptic loosening due to an inferior cementing technique at that level. In order to enhance cement penetration, Labutti et al. [1] have even suggested a technique with direct pressured cement injection at the posterior flanges. Previous studies have shown that a cement penetration depth of 3 mm is advisable and that thicker cement layers (5–10 mm) increase the risk for thermal damage [10,11]. In our study the average penetration depth of all techniques except the third was within this range. Based upon the results of our work, we conclude that technique 1, where cement was applied onto the anterior and distal bone surfaces, as well as the posterior flanges of the prosthesis, was statistically superior to the other techniques. A weakness of our study is that we did not standardize the force applied during impaction of the component nor the pressurization during the setting faze of the cement. All the cases however were subsequently performed by the same investigator (M. V.). Manual impaction of the FC was done in all cases until the inner surface of the component was in contact with the bone surface. This was controlled visually. To ensure contact until hardening of the cement, manual pressure was given for 15 min. Our study was performed using an artificial sawbone model. Sawbones were used for the sake of reproducibility, and as a result some variables which are clinically relevant are not evaluated in the study, including the effect of intramedullary bleeding and accurate surface preparation [3–6,13,14]. Previous studies have however proven the accuracy of these models in mimicking the structural properties of the natural situation, with significantly lower variability in testing compared to cadaveric specimens, and therefore offering a more reliable research model [12,15,16]. In view of this we therefore believe that our experimental set-up is valid and in view of the current technology available, probably the most appropriate for the specific question we wanted to investigate. 5. Conclusion In this study we investigated the effect of four different cementing techniques on overall cement penetration as well as length of the cement mantle. The technique which included cement application onto the anterior and distal bone surfaces, as well as the posterior
flanges of the prosthesis, was statistically superior to the other techniques. We therefore advocate this technique as the standard for cementing the femoral component in TKA. 6. Conflict of interest The first author Michael Vaninbroukx does not have any disclosure to make. Luc Labey and Bernardo Innocenti are both employees of the Smith & Nephew company. They are both working at the European Centre for Knee Research (Smith & Nephew) in Leuven, Belgium. The senior author, Johan Bellemans, is a consultant for the Smith & Nephew Company and supervises studies in the European Centre for Knee Research, Leuven, Belgium. Acknowledgment I would like to thank the Smith & Nephew company for providing all the necessary material for this study. References [1] Labutti RS, Bayers-Thering M, Krackow KA. Enhancing femoral cement fixation in total knee arthroplasty. J Arthroplasty Dec 2003;18(8):979–83. [2] King TV, Scott RD. Femoral component loosening in total knee arthroplasty. Clin Orthop Relat Res Apr 1985;194:285–90. [3] Majkowski RS, Miles AW, Bannister GC, Perkins J, Taylor GJ. Bone surface preparation in cemented joint replacement. J Bone Jt Surg, Br May 1993;75B(3):459–63. [4] Maistrelli GL, Antonelli L, Fornasier V, Mahomed N. Cement penetration with pulsed lavage versus syringe irrigation in total knee arthroplasty. Clin Orthop Relat Res Mar 1995;312:261–5. [5] Benjamin JB, Gie GA, Lee AJ, Ling RS, Volz RG. Cementing technique and the effects of bleeding. J Bone Jt Surg, Br Aug 1987;69B(4):620–4. [6] Norton MR, Eyres KS. Irrigation and suction technique to ensure reliable cement penetration for total knee arthroplasty. J Arthroplasty Jun 2000;15(4):468–74. [7] Dorr LD, Lindberg JP, Claude-Faugere M, Malluche HH. Factors influencing the intrusion of methylmethacrylate into human tibiae. Clin Orthop Relat Res Mar 1984;183:147–52. [8] Han HS, Kang SB, Yoon KS. High incidence of loosening of the femoral component in legacy posterior stabilised-flex total knee replacement. J Bone Jt Surg, Br Nov 2007;89B(11):1457–61. [9] Scuderi GR. Successful results with a high flexion posterior stabilised knee prosthesis. J Bone Jt Surg, Br Dec 21 2007 Electronic letter. [10] Huiskes R, Slooff TJ. Thermal injury of cancellous bone following pressured penetration of acrylic cement. Trans Orthop Res Soc Jun 1981;6:134. [11] Walker PS, Soudry M, Ewald FC, McVickar H. Control of cement penetration in total knee arthroplasty. Clin Orthop Relat Res 1984 May;185:155–64. [12] Heiner AD, Brown TD. Structural properties of a new design of composite replicate femurs and tibias. J Biomech Jun 2001;34(6):773–81. [13] Miller MA, Race A, Gupta S, Higham P, Clarke MT, Mann KA. The role of cement viscosity on cement–bone apposition and strength: an in vitro model with medullary bleeding. J Arthroplasty 2007 Jan;22(1):109–16. [14] Stannage K, Shakespeare D, Bulsara M. Suction technique to improve cement penetration under the tibial component in total knee arthroplasty. Knee Mar 2003;10:67–73. [15] Cristofolini L, Viceconti M. Mechanical validation of whole bone composite tibia models. J Biomech Mar 2000;33(3):279–88. [16] Cristofolini L, Viceconti M, Cappello A, Toni A. Mechanical validation of whole bone composite femur models. J Biomech Apr 1996;29(4):525–35.