Knee Surg Sports Traumatol Arthrosc DOI 10.1007/s00167-014-2957-x
KNEE
Using fibula as a reference can be beneficial for the tibial component alignment after total knee arthroplasty, a retrospective study Mehmet Erdem • Deniz Gulabi • Gultekin Sitki Cecen Cem Coskun Avci • Murat Asci • Fevzi Saglam
•
Received: 16 November 2013 / Accepted: 13 March 2014 Ó Springer-Verlag Berlin Heidelberg 2014
Abstract Purpose One of the important factors in a successful arthroplasty is component alignment. The primary objective of this study was to determine whether the fibular shaft reference technique is beneficial for the tibial component position on the postoperative plain radiograph after total knee arthroplasty. Methods A total of 42 patients between 2009 and 2011 were analysed retrospectively. The surgeon prepared the tibia using an extramedullary cutting guide and set the posterior tibial slope with respect to the fibular reference rod. In the postoperative radiographic measurements, a true anteroposterior and lateral radiograph of the lower leg covering the whole length of the tibia was used. M. Erdem Orthopaedic and Traumatology Department, Faculty of Medicine, Sakarya University, Sakarya, Turkey e-mail: [email protected] D. Gulabi (&) G. S. Cecen F. Saglam Dr. Lu¨tfi Kırdar Kartal Training and Research Hospital, Semsi Denizer Cad. E5. Yanyol Cevizli Kavsagı, Kartal, Istanbul 34890, Turkey e-mail: [email protected] G. S. Cecen e-mail: [email protected] F. Saglam e-mail: [email protected] C. C. Avci ¨ mraniye, Istanbul, Umraniye Training and Research Hospital, U Turkey e-mail: [email protected] M. Asci Tokat State Hospital, Tokat, Turkey e-mail: [email protected]
Results Five patients were excluded as they did not meet the inclusion criteria, four patients were excluded due to improper radiographs and the study group was reduced to 33 patients and 35 knees. The mean preoperative tibiofibular angle was 2.1° ± 0.8°. The mean postoperative tibial sagittal angle measurements were 83.3° ± 1.4° (81°–86°). 33 (94 %) Knees gained the desired tibial sagittal angle within the desired alignment (5° ± 3°). The mean postoperative tibial coronal angle was 89.3° ± 1.5°. The tibial component coronal angle of two knees was more than 3 alignment from the neutral mechanical axis. Conclusion The major clinical relevance of the technique described in the present study is cost-effectiveness, and it does not require any extra time or surgical equipment. This method can be used as an alternative choice for bulky extremities which is a cause of malalignment of the components. Level of evidence Retrospective case series, Level IV. Keywords
Knee Knee prothesis Alignment Fibula
Introduction The lifetime utility of a knee prosthesis depends directly on the stabilization of soft tissue and maintenance of adequate prosthesis alignment in the coronal, sagittal, and rotational axis, as determined by satisfactory bone resection [14, 15, 17, 23]. Resection over a femoral intramedullary rod is now widely accepted and is being used successfully and uneventfully for femoral resection. However, there is no consensus for the guidance of tibial resection. Some authors use an extramedullary guide, while others use an intramedullary one, computer-assisted navigation systems, and
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patient-specific cutting blocks [2, 18, 25]. All these conventional procedures have some challenges as long surgical time, high costs, intramedullary canal violation, and intramedullary pressure in the tibia, so we aimed to evaluate an alternative technique for use. The technique described here was proposed by Laskin as a choice for tibial component alignment in total knee arthroplasty (TKA) [18]. The aim of this study was to evaluate the accuracy of tibial component alignment in knee prosthetics using the fibula as a reference. The hypothesis was that using the fibula as a reference could achieve optimal accuracy in final tibial component positioning. In this study, our aim was to achieve 85° ± 3° tibial slope angle and 90° ± 3° coronal tibial tray alignment [1, 27] over an extramedullary tibial guide using the fibula as a reference.
Materials and methods A total of 42 patients who had received 45 total knee prostheses between July 2009 and November 2011 were analysed retrospectively. Nonoperative treatment had failed for these patients, and they did not have any major flexion contractures (\7°) or coronal deformity (\10° varus/valgus). The inclusion criteria for the study were as follows: a diagnosis of primary osteoarthrosis, a neutral or varus knee due to degenerative arthrosis of the knee joint, and surgery for pain resulting from arthrosis. Five patients were excluded from the study; one patient with a proximal tibial osteotomy, two patients with postinfection arthritis, and two patients with severe instability that could not treated by a cruciateretaining TKA. Varus deformities of the knees were due to intra-articular factors with loss of bone on the medial tibia plateau. No extra-articular deformities were determined in either the sagittal or coronal plane. Consequently, 40 knees of 37 patients were treated with primary TKA using the fibula as a reference. Informed consent for participation in the study was obtained from all patients. Clinical records were reviewed for demographic information (gender, age, side, height, and weight) and the primary diagnosis. Body mass index (BMI) was calculated as the weight in kilograms divided by height in metre squared (kg/m2). Surgical techniques The fibula head and lateral malleolus of each patient were marked with a sterile marking pen. All operations were performed with a medial parapatellar approach. All patients received a posterior cruciate-retaining prosthesis (Genesis 2, Smith-Nephew, Andover, Massachusetts, USA). Femoral resections were made over an intramedullary guide. Before tibial resection, the proximal head of the fibula and the lateral malleolus were identified, and a long, 8-mm-
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diameter rod was held parallel to the fibula by the assistant surgeon. The surgeon prepared the tibia using an extramedullary cutting guide and set the posterior tibial slope with respect to the fibular reference rod. The long rod of the extramedullary guide was aligned parallel to the rod that had been aligned with the fibula. The tibial resection block was aligned perpendicular to a line extending from the centre of the tibial plateau to the centre of the talus dome. The rotation was aligned with the medial 1/3 of the tibial tubercle. After obtaining sagittal, coronal, and rotational alignment, the tibia cutting block was fixed with pins and resection was made with a motorized cutter. All prostheses were fixed with cement. The patella was not resurfaced in any case. The objective of the tibial component implantation was to correct the tibial alignment to as close to neutral as possible within a range of 3 varus or valgus and 5° ± 3° tibial slope. All knees were operated on by a single surgeon (ME), so intersurgeon variation risk was minimized. Radiographic measurements Postoperative radiographs of each knee were measured to determine the proximal tibial slope angle, proximal tibial coronal angle (TCA), and mechanical axis (MA) degree. All radiographs were reviewed with the strongest criteria for adequacy. The fibular head and lesser trochanter were used as landmarks to determine excessive rotation of the limbs on the radiographs [23]. Any radiographs that showed one of these two landmarks in excess meant the limb was malrotated. Radiographs that revealed obliqueness in any plane were a cause of exclusion. Anteroposterior and lateral 14 9 17-in. image radiographs of the knee were used to determine the long axis of the tibia. All radiographic alignment measurements were taken by an independent radiographic reviewer who was blinded to the treatment. The independent observer assessed all radiographs twice with an interval of 1 week. All measured values were calculated to one decimal place. To eliminate interobserver variability, a single radiographic reviewer was used. In the measurements, a true anteroposterior and lateral radiograph of the lower leg covering the whole length of the tibia was used. In that method, the sagittal MA was defined as the connecting line between the midpoints of the tibia plateau and the tibia plafond on the lateral X-ray. A line drawn between the centre of these two reference points shows the tibia’s MA line. A line was then drawn parallel to the articular surface of the proximal tibia. The angle between the MA line and the articular surface line was designated as the tibial slope (TSA) (Fig. 1a). The TCA was determined by the intersection of a line drawn from the centre of the knee to the centre of the talus with a line drawn across the tibial component (Fig. 1b). The MA was determined by the angle of the line drawn from the
Knee Surg Sports Traumatol Arthrosc Fig. 1 Sixty-eight-year-old female patient. a Postoperative lateral radiographs of the left knee showing a tibial slope of 84. b Postoperative AP radiograph of the left knee showing tibial coronal angle of 91°
Fig. 2 Preoperative tibiofibular angle of the right lower extremity of 2.0°
centre of the femoral head to the centre of the knee to the line drawn from the centre of the knee to the centre of the talus. The fibular shaft axis (FSA) was defined as the line connecting the midpoints of the outer cortical diameter of the proximal and distal ends of the fibular diaphysis [33]. The angle between the FSA and the sagittal MA line of the tibia is the tibiofibular angle (TFA) (Fig. 2). Postoperative radiographic measurements were taken at mean postoperative 5th month. The radiographic assessments were performed according to the Knee Society Roentgenographic Evaluation System [9]. Radiological measurements were taken, using a ruler. The accuracy of the measurements cannot be more than 0.1 mm when a ruler is used. Statistical analysis All measurements were taken twice at a week apart by one independent reviewer for all patients, and the average of
these two measurements was used as the data. The statistical analysis was carried out using Number Cruncher Statistical System (NCSS) 2007 and Power Analysis and Sample Size (PASS) 2008 statistical software (NCSS Statistical Software, Utah, USA). The paired sample t test was used to test the differences between mean measurements. Descriptive statistical methods (mean, standard deviation, median, percentage, ratio) were used in the evaluation of data, and for the analysis of the relationship beween parameters, Pearson’s correlation coefficient was used. Results with p values \0.05 were considered significant. Test–retest was performed for intraobserver reliability with the observer taking the measurements again after 1 week in all cases. The number of outliers in this study, defined as tibial component alignment outside of 90° ± 3° in the coronal plane, a tibial posterior slope outside of 85° ± 3° in the sagittal plane, and lower extremity mechanical alignment outside of 3° of the neutral MA, were determined. Positions of the femoral and tibial components that fell within the above parameters were considered to be in the optimal position.
Results The median age of the patients was 67 years (range 63–75). Five patients were excluded as they did not meet the inclusion criteria, 4 patients were excluded due to improper radiographs, and the study group was reduced to 33 patients and 35 knees. The male to female ratio was 2:1 (22 female, 11 male). Twenty-five knees had Kellgren–Lawrence [5] grade 3 knee arthrosis, and 10 had grade 4. The knees operations were 25 right side and 10 left side. Osteoarthritis was the primary diagnosis in all knees (Table 1).
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Knee Surg Sports Traumatol Arthrosc Table 1 Demographic data N
%
Table 3 Relationship of HSS scores with Age, BMI, and tibial component angles Postop HSS R
Gender Male
22
66.7
Female
11
33.3
Side Right
24
68.6
Left
11
31.4
3
25
71.4
4
10
28.6
Grade
BMI \25 25–30
6 13
18.2 39.4
[30
14
42.4
Table 2 Radiographic measurements and HSS results Min–Max
Mean ± SD
Age
63–75
67.5 ± 3.23
BMI
22.9–45
32.4 ± 6.41
1.3–3.1
2.1 ± 0.83
Preop TFA Postop tibial sagittal angle
81–86
83.32 ± 1.39
Postop coronal tibial angle
84–92
89.32 ± 1.47
174–183
179.4 ± 2.26
Preop HSS
Postop mechanical axis
54–76
64.7 ± 10.3
Postop HSS
88–100
95.1 ± 4.2
The mean BMI was 32.4 kg/m2 (range 22.9–45 kg/m2). Six (18 %) patients were normal weight (18.5–24.9 kg/ m2), 13 (40 %) patients were overweight (BMI 25–29.9 kg/m2), and 14 (42 %) patients were obese (BMI [30). There was no statistically significant difference between radiographic values in respect of BMI (p [ 0.05). The mean preoperative TFA was 2.1° ± 0.8° (range 1.3°–3.1°). The mean postoperative tibial sagittal angle measurements were 83.3° ± 1. 4° (range 81°–86°). Thirtythree (94 %) knees gained the desired tibial sagittal angle within the desired alignment (5° ± 3°). The tibial slope angle of 2 (6 %) knees was out of the target range. The mean postoperative TCA was 89.3° ± 1.5° (range 84°– 92°). The intraclass correlation coefficient was 0.88 for TFA, 0.92 for TSA, 0.93 for TCA, and 0.90 for MAA. The tibial component coronal angle of two knees was more than 3° alignment from the neutral MA. One of these knees had grade 3 gonarthrosis and BMI of obesity, and the other knee had grade 4 gonarthrosis and normal BMI. The mean MA angle was 179.4 (range 174°–183°) as measured on the postoperative standing orthorontgeonagraphic images (Table 2).
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Age
0.145
BMI (kg/m2)
0.002
Postop tibial sagittal angle Postop coronal tibial angle
0.249 0.305
Postop mechanical axis
0.343
R Pearson’s correlation cofficient
The mean preoperative HSS knee score [11] was 64.7 ± 10.3. The mean final follow-up HSS knee score was 95.1 ± 4.2. No intraoperative complications were noted in this study group. Superficial infection was observed in two cases in the early postoperative period, and these were resolved with wound care. There was no statistically significant correlation between the final follow-up HSS knee scores and age, BMI, and radiological TSA, TCA, MA, and FSA (p [ 0.05) (Table 3).
Discussion To the best of our knowledge, this is first study to have examined the postoperative tibial component accuracy using the fibula as a reference. The most important of the findings of the present study were that coronal and sagittal alignment of the tibial component could be achieved with the present technique, which was first proposed by Laskin [18], and has been described above. Previous studies have reported success rates of 65–95.8 % for tibial component coronal alignment within the target alignment [16, 19, 20, 24, 26, 27, 31]. In the current study, coronal tibial component alignment of 90° ± 3° was achieved in 94 % of the knees. There were two outliers. One of these knees had grade 3 gonarthrosis and BMI of obesity, and the other knee had grade 4 gonarthrosis and normal BMI. That, there were no severe extra-articular deformities in the operated knees and all the operations were performed by a single experienced surgeon can be said to have contributed to our success. However, intramedullary instrumentation has a deleterious effect as it can increase the intramedullary pressure in the tibia, which can lead to the risk of embolization [6, 28]. Moreover, in elderly and osteoporotic patients, the proximal metaphysis of the tibia is wide and the cortex is thin so there is a high risk of malalignment. To avoid these risks, the intramedullary technique was not used in the current study. The posterior tibial slope after knee prosthesis operations has a direct effect on anteroposterior stability, knee
Knee Surg Sports Traumatol Arthrosc
joint range of motion, and contact pressure inside the joint [3, 12, 13, 32]. Previous studies have reported success rates of 72.1–94 % for tibial component sagittal alignment within the target alignment [24, 27, 31]. In the current study, we achieved 94 % of the tibial slope of the tibial component within the target degrees (85° ± 3°). There were two outliers. One of these knees had grade 4 gonarthrosis and BMI of obesity, and the other had grade 3 gonarthrosis and normal BMI. Berend et al. [4] and Seo et al. [29] demonstrated that patients with BMI greater than 33.7 kg/m2 were at risk of postoperative malalignment. However, in the current study, only two knees had varus alignment, one of which was obese. Although the fibula was marked under fluoroscopy, in obese patients, bulky extremities will be a cause of malalignment of the extramedullary guides. Therefore, the fluoroscopy control of the fibula in obese patients requires particular attention. For the management of limb alignment, standing lower extremity orthorontgenographs are the gold standard. More reliable measurements can be obtained from full lower extremity CT scans [17] although that entails radiation exposure and high costs. It was critical to take scans, so we used 14 9 17 in. images and standing lower extremity orthorontgenography for the measurement, as recommended by Skytta et al. [30] stated. In previous studies, Mason et al. [20] demonstrated 68.2 %, Nam et al. [24] 74.5 %, and Roh et al. [27] 90 % of total knee arthroplasties performed using conventional techniques to be within 3 of neutral alignment. In the present study, 94 % of total knee arthroplasties were aligned within 3 of neutral mechanical alignment. We concluded this to be due to careful planning on the orthoroentography AP/LAT radiographs which were taken in a standing position and no femoral and tibial deformities which may cause malalignment. Computer-assisted navigation systems have been used to achieve accuracy of component alignment in TKA, but conflicting results have been reported [2, 8, 25]. In a multicentre, prospective randomized study, Barrett et al. [2] reported that there was a statistically significant difference between a conventional extramedullary guide system and a computer-assisted navigation system only in tibial component coronal alignment, with no statistically significant improvement in the MA, femoral coronal, sagittal, and tibial sagittal alignment. However, clinical outcomes and postoperative ROM are influenced by various factors, such as the severity of the preoperative deformity, alteration of posterior femoral offset, flexion angle of the femoral component, and the tension of the soft tissues (PCL). In the current study, an improvement was seen in the HSS knee score [11]. We believe that this improvement is due to the postoperative component alignment obtained at the desired values, and
none of the patients had major flexion contracture or coronal deformities. There was no statistically significant correlation between the postoperative tibial sagittal angle, TCA, or mechanical angle with the final follow-up HSS scores (p [ 0.05). The major clinical relevance of the technique described in the present study was cost-effectiveness when compared with computer-assisted TKA and patient-specific guides, which are time-consuming to prepare. Avoidance of intramedullary canal violation and intramedullary pressure in the tibia, which can cause a risk of embolization, are the other advantages of this technique. Bulky extremities are a cause of malalignment in TKA using extramedullary guides. Matziolis et al. [22] stated that tibial component alignment according to the ankle joint or second metatarsal is problematic. The references of the bone prominence are not palpable, but in the present study, the reference rod of the fibula was managed under fluoroscopy. Therefore, this technique could be used as an alternative choice for bulky extremities. This study has some limitations. First, anatomical features of the tibia and fibula can vary with the ethnic origin of the study group [7, 10, 21]. All the patients in the current study were ethnically from the north of Turkey, and it might be wrong to reflect our findings of TFA to a population of different ethnic origin. Second, this study did not have a comparison group to examine the accuracy of the technique used. Third, this was a radiographic study of component alignment so an improper radiographic technique may lead to measurement errors. Finally, all measurements were taken by an independent reviewer with a ruler, so there might have been some measurement bias. The retrospective nature of the study and low number of the sample group were other limitations. Conclusion This study demonstrates that a fibula reference-assisted technique reduces the number of outliers for tibial component alignment and MA alignment. This technique can be preferable as costs are low, and it does not require any extra time or surgical equipment. Conflict of interest No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript.
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Knee Surg Sports Traumatol Arthrosc 2. Barrett WP, Mason JB, Moskal JT, Dalury DF, Oliashirazi A, Fisher DA (2011) Comparison of radiographic alignment of imageless computer-assisted surgery vs conventional instrumentation in primary total knee arthroplasty. J Arthroplast 26: 1273–1284 3. Bellemans J, Robijns F, Duerinckx J, Banks S, Vandenneucker H (2005) The influence of tibial slope on maximal flexion after total knee arthroplasty-. Knee Surg Sports Traumatol Arthrosc 13:193–196 4. Berend ME, Ritter MA, Meding JB, Faris PM, Keating EM, Redelman R, Faris GW, Davis KE (2004) Tibial component failure mechanisms in total knee arthroplasty. Clin Orthop Relat Res 428:26–34 5. Brandt KD, Fife RS, Braunstein EM, Katz B (1991) Radiographic grading of the severity of knee osteoarthritis: relation of the Kellgren and Lawrence grade to a grade based on joint space narrowing, and correlation with arthroscopic evidence of articular cartilage degeneration-. Arthritis Rheum 34:1381–1386 6. Byrick RJ, Forbes D, Waddell JP (1986) A monitored cardiovascular collapse during cemented total knee replacement. Anesthesiology 65:213–216 7. Chiu KY, Zhang SD, Zhang GH (2000) Posterior slope of tibial plateau in Chinese. J Arthroplast 15:224–227 8. Choi WC, Lee S, An JH, Kim D, Seong SC, Lee MC (2011) Plain radiograph fails to reflect the alignment and advantages of navigation in total knee arthroplasty. J Arthroplast 26:756–764 9. Ewald FC (1989) The Knee Society total knee arthroplasty roentgenographic evaluation and scoring system. Clin Orthop Relat Res 248:9–12 10. Hofmann AA, Bachus KN, Wyatt RW (1991) Effect of the tibial cut on subsidence following total knee arthroplasty. Clin Orthop Relat Res 269:63–69 11. Insall JN, Ranawat CS, Aglietti P, Shine J (1976) A comparison of four models of total knee-replacement prostheses. J Bone Jt Surg Am 58:754–765 12. Iorio R, Bolle G, Conteduca F, Valeo L, Conteduca J, Mazza D, Ferretti A (2013) Accuracy of manual instrumentation of tibial cutting guide in total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc 21:2296–2300 13. Kansara D, Markel DC (2006) The effect of posterior tibial slope on range of motion after total knee arthroplasty. J Arthroplast 21:809–813 14. Karade V, Ravi B, Agarwal M (2012) Extramedullary versus intramedullary tibial cutting guides in megaprosthetic total knee replacement. J Orthop Surg Res 2(7):33 15. Kawahara S, Okazaki K, Matsuda S, Mitsuyasu H, Nakahara H, Okamoto S, Iwamoto Y (2013) Medial sixth of the patellar tendon at the tibial attachment is useful fort he anterior reference in rotational alignment of the tibial component. Knee Surg Sports Traumatol Arthrosc. Mar 12. PMID: 23479057 (Epub ahead of print) 16. Keyes BJ, Markel DC, Meneghini RM (2013) Evaluation of limb alignment, component positioning, and function in primary total knee arthroplasty using a pinless navigation technique compared with conventional methods. J Knee Surg 26:127–132 17. Kim SJ, MacDonald M, Hernandez J, Wixson RL (2005) Computer assisted navigation in total knee arthroplasty: improved coronal alignment. J Arthroplast 20:123–131
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18. Laskin RS (2003) Instrumentation pitfalls. J Arthroplast 18:18–22 19. Maestro A, Harwin SF, Sandoval MG, Vaquero DH, Murcia A (1998) Influence of intramedullary versus extramedullary alignment guides on final total knee arthroplasty component position: a radiographic analysis. J Arthroplast 13:552–558 20. Mason JB, Fehring TK, Estok R, Banel D, Fahrbach K (2007) Meta-analysis of alignment outcomes in computer-assisted total knee arthroplasty surgery. J Arthroplast 22:1097–1106 21. Matsuda S, Miura H, Nagamine R, Urabe K, Ikenoue T, Okazaki K, Iwamoto Y (1999) Posterior tibial slope in the normal and varus knee. Am J Knee Surg 12:165–168 22. Matziolis G, Pfitzner T, Thiele K, Matziolis D, Perka C (2011) Influence of the position of the fibular head after ımplantation of a total knee prothesis on femorotibial rotation. Orthopedics 34:e610–e614 23. Mullaji AB, Shetty GM, Lingaraju AP, Bhayde S (2013) Which factors increase risk of malalignment of the hip–knee–ankle axis in TKA? Clin Orthop Relat Res 471:134–141 24. Nam D, Cody EA, Nguyen JT, Figgie MP, Mayman DJ (2014) Extramedullary guides versus portable, accelerometer-based navigation for tibial alignment in total knee arthroplasty: a randomized, controlled trial. J Arthroplast 29:288–294 25. Nunley RM, Ellison BS, Ruh EL, Williams BM, Foreman K, Ford AD, Barrack RL (2012) Are patient-specific cutting blocks cost-effective for total knee arthroplasty? Clin Orthop Relat Res 470:889–894 26. Reed MR, Bliss W, Sher JL, Emmerson KP, Jones SM, Partington PF (2002) Extramedullary or intramedullary tibial alignment guides: a randomised, prospective trial of radiological alignment. J Bone Jt Surg Br 84:858–860 27. Roh YW, Kim TW, Lee S, Seong SC, Lee MC (2013) Is TKA using patient-specific ınstruments comparable to conventional TKA? A randomized controlled study of one system. Clin Orthop Relat Res. doi:10.1007/s11999-013-3206-1 28. Samii K, Elmelik E, Mourtada MB, Debeyre J, Rapin M (1979) Intraoperative hemodynamic changes during total knee replacement. Anesthesiology 50:239–242 29. Seo JG, Moon YW, Park SH, Shim JW, Kim SM (2012) An alternative method to create extramedullary references in total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc 20:1339–1348 30. Skytta¨ ET, Lohman M, Tallroth K, Remes V (2009) Comparison of standard anteroposterior knee and hip-to-ankle radiographs in determining the lower limb and implant alignment after total knee arthroplasty. Scand J Surg 98:250–253 31. Song EK, Seon JK, Yim JH, Netravali NA, Bargar WL (2013) Robotic-assisted TKA reduces postoperative alignment outliers and improves gap balance compared to conventional TKA. Clin Orthop Relat Res 471:118–126 32. Whiteside LA, Amador DD (1988) The effect of posterior tibial slope on knee stability after ortholoc total knee arthroplasty. J Arthroplast 3:51–57 33. Yoo JH, Chang CB, Shin KS, Seong SC, Kim TK (2008) Anatomical references to assess the posterior tibial slope in total knee arthroplasty: a comparison of 5 anatomical axes. J Arthroplast 23:586–592
KNEE
Using fibula as a reference can be beneficial for the tibial component alignment after total knee arthroplasty, a retrospective study Mehmet Erdem • Deniz Gulabi • Gultekin Sitki Cecen Cem Coskun Avci • Murat Asci • Fevzi Saglam
•
Received: 16 November 2013 / Accepted: 13 March 2014 Ó Springer-Verlag Berlin Heidelberg 2014
Abstract Purpose One of the important factors in a successful arthroplasty is component alignment. The primary objective of this study was to determine whether the fibular shaft reference technique is beneficial for the tibial component position on the postoperative plain radiograph after total knee arthroplasty. Methods A total of 42 patients between 2009 and 2011 were analysed retrospectively. The surgeon prepared the tibia using an extramedullary cutting guide and set the posterior tibial slope with respect to the fibular reference rod. In the postoperative radiographic measurements, a true anteroposterior and lateral radiograph of the lower leg covering the whole length of the tibia was used. M. Erdem Orthopaedic and Traumatology Department, Faculty of Medicine, Sakarya University, Sakarya, Turkey e-mail: [email protected] D. Gulabi (&) G. S. Cecen F. Saglam Dr. Lu¨tfi Kırdar Kartal Training and Research Hospital, Semsi Denizer Cad. E5. Yanyol Cevizli Kavsagı, Kartal, Istanbul 34890, Turkey e-mail: [email protected] G. S. Cecen e-mail: [email protected] F. Saglam e-mail: [email protected] C. C. Avci ¨ mraniye, Istanbul, Umraniye Training and Research Hospital, U Turkey e-mail: [email protected] M. Asci Tokat State Hospital, Tokat, Turkey e-mail: [email protected]
Results Five patients were excluded as they did not meet the inclusion criteria, four patients were excluded due to improper radiographs and the study group was reduced to 33 patients and 35 knees. The mean preoperative tibiofibular angle was 2.1° ± 0.8°. The mean postoperative tibial sagittal angle measurements were 83.3° ± 1.4° (81°–86°). 33 (94 %) Knees gained the desired tibial sagittal angle within the desired alignment (5° ± 3°). The mean postoperative tibial coronal angle was 89.3° ± 1.5°. The tibial component coronal angle of two knees was more than 3 alignment from the neutral mechanical axis. Conclusion The major clinical relevance of the technique described in the present study is cost-effectiveness, and it does not require any extra time or surgical equipment. This method can be used as an alternative choice for bulky extremities which is a cause of malalignment of the components. Level of evidence Retrospective case series, Level IV. Keywords
Knee Knee prothesis Alignment Fibula
Introduction The lifetime utility of a knee prosthesis depends directly on the stabilization of soft tissue and maintenance of adequate prosthesis alignment in the coronal, sagittal, and rotational axis, as determined by satisfactory bone resection [14, 15, 17, 23]. Resection over a femoral intramedullary rod is now widely accepted and is being used successfully and uneventfully for femoral resection. However, there is no consensus for the guidance of tibial resection. Some authors use an extramedullary guide, while others use an intramedullary one, computer-assisted navigation systems, and
123
Knee Surg Sports Traumatol Arthrosc
patient-specific cutting blocks [2, 18, 25]. All these conventional procedures have some challenges as long surgical time, high costs, intramedullary canal violation, and intramedullary pressure in the tibia, so we aimed to evaluate an alternative technique for use. The technique described here was proposed by Laskin as a choice for tibial component alignment in total knee arthroplasty (TKA) [18]. The aim of this study was to evaluate the accuracy of tibial component alignment in knee prosthetics using the fibula as a reference. The hypothesis was that using the fibula as a reference could achieve optimal accuracy in final tibial component positioning. In this study, our aim was to achieve 85° ± 3° tibial slope angle and 90° ± 3° coronal tibial tray alignment [1, 27] over an extramedullary tibial guide using the fibula as a reference.
Materials and methods A total of 42 patients who had received 45 total knee prostheses between July 2009 and November 2011 were analysed retrospectively. Nonoperative treatment had failed for these patients, and they did not have any major flexion contractures (\7°) or coronal deformity (\10° varus/valgus). The inclusion criteria for the study were as follows: a diagnosis of primary osteoarthrosis, a neutral or varus knee due to degenerative arthrosis of the knee joint, and surgery for pain resulting from arthrosis. Five patients were excluded from the study; one patient with a proximal tibial osteotomy, two patients with postinfection arthritis, and two patients with severe instability that could not treated by a cruciateretaining TKA. Varus deformities of the knees were due to intra-articular factors with loss of bone on the medial tibia plateau. No extra-articular deformities were determined in either the sagittal or coronal plane. Consequently, 40 knees of 37 patients were treated with primary TKA using the fibula as a reference. Informed consent for participation in the study was obtained from all patients. Clinical records were reviewed for demographic information (gender, age, side, height, and weight) and the primary diagnosis. Body mass index (BMI) was calculated as the weight in kilograms divided by height in metre squared (kg/m2). Surgical techniques The fibula head and lateral malleolus of each patient were marked with a sterile marking pen. All operations were performed with a medial parapatellar approach. All patients received a posterior cruciate-retaining prosthesis (Genesis 2, Smith-Nephew, Andover, Massachusetts, USA). Femoral resections were made over an intramedullary guide. Before tibial resection, the proximal head of the fibula and the lateral malleolus were identified, and a long, 8-mm-
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diameter rod was held parallel to the fibula by the assistant surgeon. The surgeon prepared the tibia using an extramedullary cutting guide and set the posterior tibial slope with respect to the fibular reference rod. The long rod of the extramedullary guide was aligned parallel to the rod that had been aligned with the fibula. The tibial resection block was aligned perpendicular to a line extending from the centre of the tibial plateau to the centre of the talus dome. The rotation was aligned with the medial 1/3 of the tibial tubercle. After obtaining sagittal, coronal, and rotational alignment, the tibia cutting block was fixed with pins and resection was made with a motorized cutter. All prostheses were fixed with cement. The patella was not resurfaced in any case. The objective of the tibial component implantation was to correct the tibial alignment to as close to neutral as possible within a range of 3 varus or valgus and 5° ± 3° tibial slope. All knees were operated on by a single surgeon (ME), so intersurgeon variation risk was minimized. Radiographic measurements Postoperative radiographs of each knee were measured to determine the proximal tibial slope angle, proximal tibial coronal angle (TCA), and mechanical axis (MA) degree. All radiographs were reviewed with the strongest criteria for adequacy. The fibular head and lesser trochanter were used as landmarks to determine excessive rotation of the limbs on the radiographs [23]. Any radiographs that showed one of these two landmarks in excess meant the limb was malrotated. Radiographs that revealed obliqueness in any plane were a cause of exclusion. Anteroposterior and lateral 14 9 17-in. image radiographs of the knee were used to determine the long axis of the tibia. All radiographic alignment measurements were taken by an independent radiographic reviewer who was blinded to the treatment. The independent observer assessed all radiographs twice with an interval of 1 week. All measured values were calculated to one decimal place. To eliminate interobserver variability, a single radiographic reviewer was used. In the measurements, a true anteroposterior and lateral radiograph of the lower leg covering the whole length of the tibia was used. In that method, the sagittal MA was defined as the connecting line between the midpoints of the tibia plateau and the tibia plafond on the lateral X-ray. A line drawn between the centre of these two reference points shows the tibia’s MA line. A line was then drawn parallel to the articular surface of the proximal tibia. The angle between the MA line and the articular surface line was designated as the tibial slope (TSA) (Fig. 1a). The TCA was determined by the intersection of a line drawn from the centre of the knee to the centre of the talus with a line drawn across the tibial component (Fig. 1b). The MA was determined by the angle of the line drawn from the
Knee Surg Sports Traumatol Arthrosc Fig. 1 Sixty-eight-year-old female patient. a Postoperative lateral radiographs of the left knee showing a tibial slope of 84. b Postoperative AP radiograph of the left knee showing tibial coronal angle of 91°
Fig. 2 Preoperative tibiofibular angle of the right lower extremity of 2.0°
centre of the femoral head to the centre of the knee to the line drawn from the centre of the knee to the centre of the talus. The fibular shaft axis (FSA) was defined as the line connecting the midpoints of the outer cortical diameter of the proximal and distal ends of the fibular diaphysis [33]. The angle between the FSA and the sagittal MA line of the tibia is the tibiofibular angle (TFA) (Fig. 2). Postoperative radiographic measurements were taken at mean postoperative 5th month. The radiographic assessments were performed according to the Knee Society Roentgenographic Evaluation System [9]. Radiological measurements were taken, using a ruler. The accuracy of the measurements cannot be more than 0.1 mm when a ruler is used. Statistical analysis All measurements were taken twice at a week apart by one independent reviewer for all patients, and the average of
these two measurements was used as the data. The statistical analysis was carried out using Number Cruncher Statistical System (NCSS) 2007 and Power Analysis and Sample Size (PASS) 2008 statistical software (NCSS Statistical Software, Utah, USA). The paired sample t test was used to test the differences between mean measurements. Descriptive statistical methods (mean, standard deviation, median, percentage, ratio) were used in the evaluation of data, and for the analysis of the relationship beween parameters, Pearson’s correlation coefficient was used. Results with p values \0.05 were considered significant. Test–retest was performed for intraobserver reliability with the observer taking the measurements again after 1 week in all cases. The number of outliers in this study, defined as tibial component alignment outside of 90° ± 3° in the coronal plane, a tibial posterior slope outside of 85° ± 3° in the sagittal plane, and lower extremity mechanical alignment outside of 3° of the neutral MA, were determined. Positions of the femoral and tibial components that fell within the above parameters were considered to be in the optimal position.
Results The median age of the patients was 67 years (range 63–75). Five patients were excluded as they did not meet the inclusion criteria, 4 patients were excluded due to improper radiographs, and the study group was reduced to 33 patients and 35 knees. The male to female ratio was 2:1 (22 female, 11 male). Twenty-five knees had Kellgren–Lawrence [5] grade 3 knee arthrosis, and 10 had grade 4. The knees operations were 25 right side and 10 left side. Osteoarthritis was the primary diagnosis in all knees (Table 1).
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Knee Surg Sports Traumatol Arthrosc Table 1 Demographic data N
%
Table 3 Relationship of HSS scores with Age, BMI, and tibial component angles Postop HSS R
Gender Male
22
66.7
Female
11
33.3
Side Right
24
68.6
Left
11
31.4
3
25
71.4
4
10
28.6
Grade
BMI \25 25–30
6 13
18.2 39.4
[30
14
42.4
Table 2 Radiographic measurements and HSS results Min–Max
Mean ± SD
Age
63–75
67.5 ± 3.23
BMI
22.9–45
32.4 ± 6.41
1.3–3.1
2.1 ± 0.83
Preop TFA Postop tibial sagittal angle
81–86
83.32 ± 1.39
Postop coronal tibial angle
84–92
89.32 ± 1.47
174–183
179.4 ± 2.26
Preop HSS
Postop mechanical axis
54–76
64.7 ± 10.3
Postop HSS
88–100
95.1 ± 4.2
The mean BMI was 32.4 kg/m2 (range 22.9–45 kg/m2). Six (18 %) patients were normal weight (18.5–24.9 kg/ m2), 13 (40 %) patients were overweight (BMI 25–29.9 kg/m2), and 14 (42 %) patients were obese (BMI [30). There was no statistically significant difference between radiographic values in respect of BMI (p [ 0.05). The mean preoperative TFA was 2.1° ± 0.8° (range 1.3°–3.1°). The mean postoperative tibial sagittal angle measurements were 83.3° ± 1. 4° (range 81°–86°). Thirtythree (94 %) knees gained the desired tibial sagittal angle within the desired alignment (5° ± 3°). The tibial slope angle of 2 (6 %) knees was out of the target range. The mean postoperative TCA was 89.3° ± 1.5° (range 84°– 92°). The intraclass correlation coefficient was 0.88 for TFA, 0.92 for TSA, 0.93 for TCA, and 0.90 for MAA. The tibial component coronal angle of two knees was more than 3° alignment from the neutral MA. One of these knees had grade 3 gonarthrosis and BMI of obesity, and the other knee had grade 4 gonarthrosis and normal BMI. The mean MA angle was 179.4 (range 174°–183°) as measured on the postoperative standing orthorontgeonagraphic images (Table 2).
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Age
0.145
BMI (kg/m2)
0.002
Postop tibial sagittal angle Postop coronal tibial angle
0.249 0.305
Postop mechanical axis
0.343
R Pearson’s correlation cofficient
The mean preoperative HSS knee score [11] was 64.7 ± 10.3. The mean final follow-up HSS knee score was 95.1 ± 4.2. No intraoperative complications were noted in this study group. Superficial infection was observed in two cases in the early postoperative period, and these were resolved with wound care. There was no statistically significant correlation between the final follow-up HSS knee scores and age, BMI, and radiological TSA, TCA, MA, and FSA (p [ 0.05) (Table 3).
Discussion To the best of our knowledge, this is first study to have examined the postoperative tibial component accuracy using the fibula as a reference. The most important of the findings of the present study were that coronal and sagittal alignment of the tibial component could be achieved with the present technique, which was first proposed by Laskin [18], and has been described above. Previous studies have reported success rates of 65–95.8 % for tibial component coronal alignment within the target alignment [16, 19, 20, 24, 26, 27, 31]. In the current study, coronal tibial component alignment of 90° ± 3° was achieved in 94 % of the knees. There were two outliers. One of these knees had grade 3 gonarthrosis and BMI of obesity, and the other knee had grade 4 gonarthrosis and normal BMI. That, there were no severe extra-articular deformities in the operated knees and all the operations were performed by a single experienced surgeon can be said to have contributed to our success. However, intramedullary instrumentation has a deleterious effect as it can increase the intramedullary pressure in the tibia, which can lead to the risk of embolization [6, 28]. Moreover, in elderly and osteoporotic patients, the proximal metaphysis of the tibia is wide and the cortex is thin so there is a high risk of malalignment. To avoid these risks, the intramedullary technique was not used in the current study. The posterior tibial slope after knee prosthesis operations has a direct effect on anteroposterior stability, knee
Knee Surg Sports Traumatol Arthrosc
joint range of motion, and contact pressure inside the joint [3, 12, 13, 32]. Previous studies have reported success rates of 72.1–94 % for tibial component sagittal alignment within the target alignment [24, 27, 31]. In the current study, we achieved 94 % of the tibial slope of the tibial component within the target degrees (85° ± 3°). There were two outliers. One of these knees had grade 4 gonarthrosis and BMI of obesity, and the other had grade 3 gonarthrosis and normal BMI. Berend et al. [4] and Seo et al. [29] demonstrated that patients with BMI greater than 33.7 kg/m2 were at risk of postoperative malalignment. However, in the current study, only two knees had varus alignment, one of which was obese. Although the fibula was marked under fluoroscopy, in obese patients, bulky extremities will be a cause of malalignment of the extramedullary guides. Therefore, the fluoroscopy control of the fibula in obese patients requires particular attention. For the management of limb alignment, standing lower extremity orthorontgenographs are the gold standard. More reliable measurements can be obtained from full lower extremity CT scans [17] although that entails radiation exposure and high costs. It was critical to take scans, so we used 14 9 17 in. images and standing lower extremity orthorontgenography for the measurement, as recommended by Skytta et al. [30] stated. In previous studies, Mason et al. [20] demonstrated 68.2 %, Nam et al. [24] 74.5 %, and Roh et al. [27] 90 % of total knee arthroplasties performed using conventional techniques to be within 3 of neutral alignment. In the present study, 94 % of total knee arthroplasties were aligned within 3 of neutral mechanical alignment. We concluded this to be due to careful planning on the orthoroentography AP/LAT radiographs which were taken in a standing position and no femoral and tibial deformities which may cause malalignment. Computer-assisted navigation systems have been used to achieve accuracy of component alignment in TKA, but conflicting results have been reported [2, 8, 25]. In a multicentre, prospective randomized study, Barrett et al. [2] reported that there was a statistically significant difference between a conventional extramedullary guide system and a computer-assisted navigation system only in tibial component coronal alignment, with no statistically significant improvement in the MA, femoral coronal, sagittal, and tibial sagittal alignment. However, clinical outcomes and postoperative ROM are influenced by various factors, such as the severity of the preoperative deformity, alteration of posterior femoral offset, flexion angle of the femoral component, and the tension of the soft tissues (PCL). In the current study, an improvement was seen in the HSS knee score [11]. We believe that this improvement is due to the postoperative component alignment obtained at the desired values, and
none of the patients had major flexion contracture or coronal deformities. There was no statistically significant correlation between the postoperative tibial sagittal angle, TCA, or mechanical angle with the final follow-up HSS scores (p [ 0.05). The major clinical relevance of the technique described in the present study was cost-effectiveness when compared with computer-assisted TKA and patient-specific guides, which are time-consuming to prepare. Avoidance of intramedullary canal violation and intramedullary pressure in the tibia, which can cause a risk of embolization, are the other advantages of this technique. Bulky extremities are a cause of malalignment in TKA using extramedullary guides. Matziolis et al. [22] stated that tibial component alignment according to the ankle joint or second metatarsal is problematic. The references of the bone prominence are not palpable, but in the present study, the reference rod of the fibula was managed under fluoroscopy. Therefore, this technique could be used as an alternative choice for bulky extremities. This study has some limitations. First, anatomical features of the tibia and fibula can vary with the ethnic origin of the study group [7, 10, 21]. All the patients in the current study were ethnically from the north of Turkey, and it might be wrong to reflect our findings of TFA to a population of different ethnic origin. Second, this study did not have a comparison group to examine the accuracy of the technique used. Third, this was a radiographic study of component alignment so an improper radiographic technique may lead to measurement errors. Finally, all measurements were taken by an independent reviewer with a ruler, so there might have been some measurement bias. The retrospective nature of the study and low number of the sample group were other limitations. Conclusion This study demonstrates that a fibula reference-assisted technique reduces the number of outliers for tibial component alignment and MA alignment. This technique can be preferable as costs are low, and it does not require any extra time or surgical equipment. Conflict of interest No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript.
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