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High Femoral Anteversion Is Related to Femoral Trochlea Dysplasia
High Femoral Anteversion Is Related to Femoral Trochlea Dysplasia Michael Christian Liebensteiner, M.D., Ph.D., Julia Ressler, Gerd Seitlinger, M.D., Tanja Djurdjevic, M.D., Rene El Attal, M.D., and Peter Wilhelm Ferlic, M.D.
Purpose: To investigate the possible relation between femoral anteversion (AV) and trochlear morphology. Methods: Among 560 available lower-limb computed tomography (CT) scans, those with previous fracture, arthroplasty, or osteotomy were excluded and 40 cases were randomly selected. The following 4 lines were determined from the CT scans: 1 through the center of the femoral head and neck; 1 through the lesser trochanter and the center of the femoral shaft; 1 as a tangent to the dorsal part of the distal femur, just above the gastrocnemius insertion; and 1 as a tangent to the posterior condyles. Between the respective lines, the following parameters of femoral AV were determined: (1) total AV, (2) proximal AV, (3) diaphyseal AV, and (4) distal AV. Trochlea parameters were determined from 2 separate axial CT slices (proximal trochlea and 5 mm farther distally): trochlea height (medial, central, lateral), transverse trochlea shift, trochlea depth, sulcus angle, lateral trochlea slope, and Dejour trochlea type. To prove or disprove our study hypothesis, a correlation analysis was performed between the variables of AV and trochlear morphology. Results: The total AV was significantly correlated with the trochlea parameters trochlea depth (P ¼ .032), sulcus angle (P ¼ .05), and lateral trochlea slope (P ¼ .001). The diaphyseal AV was significantly correlated with the sulcus angle (P ¼ .009). The distal AV showed significant correlations with medial, central, and lateral trochlea height (.005 < P < .032) and with Dejour trochlea type (P ¼ .043). Conclusions: The morphology of the trochlea is significantly related to femoral AV. Increased AV is associated with a flatter, more dysplastic trochlea. This was particularly true for AV located at the distal femur. Level of Evidence: Level III, diagnostic study of nonconsecutive patients.
n the clinical field of patellofemoral disorders, limb alignment in the transverse plane is a regular topic of discussion. It was reported that many disorders of the patellofemoral joint (PFJ) (patellofemoral pain, patellofemoral instability, and lateral patellofemoral hypercompression) are associated with abnormal femoral anteversion (AV).1-3 In addition, disorders of the PFJ
I
From the Department of Orthopaedic Surgery (M.C.L., P.W.F.), Center of Diagnostic Radiology (T.D.) and Department of Traumatology (R.E.A.), Medical University of Innsbruck, Innsbruck; Medical University of Innsbruck (J.R.), Innsbruck; and Department of Orthopaedic Surgery, Krankenhaus Oberndorf (G.S.), Oberndorf bei Salzburg, Austria. The authors report that they have no conflicts of interest in the authorship and publication of this article. The abstract of this study has been selected as the winner of the ISAKOS (International Society of Arthroscopy, Knee Surgery & Orthopaedic Sports Medicine) Patellofemoral Research Excellence Award 2015. Received July 31, 2015; accepted March 15, 2016. Address correspondence to Peter Wilhelm Ferlic, M.D., Medical University of Innsbruck, Anichstrasse 35, 6020 Innsbruck, Austria. E-mail: peter.ferlic@ gmail.com Ó 2016 by the Arthroscopy Association of North America 0749-8063/15717/$36.00 http://dx.doi.org/10.1016/j.arthro.2016.03.023
are often related to abnormal morphology of the femoral trochlea.4-6 Therefore, it might also be speculated that femoral AV could be directly linked to trochlear morphology. This is because increased femoral AV can be expected to be accompanied by an increased Q angle, which would make greater demands on the lateral facet and fewer demands on the medial facet, thus changing the morphology of the trochlea during growth. However, previous researchers rarely dealt with the relation between femoral AV and trochlear morphology.7,8 Given the insufficient knowledge available in the literature, the purpose of this study was to investigate the possible relation between femoral AV and trochlear morphology. We hypothesized that widely accepted parameters of trochlear morphology would show significant correlations with parameters of femoral AV.
Methods After we obtained the approval of the ethics committee of our medical university, a retrospective analysis was conducted of all lower-limb computed tomography (CT) scans available in our university
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hospital’s picture archiving and communication system (PACS) performed between August 1996 and February 2013. Multislice CT images of lower limbs had been made with a helical scan technique, without contrast media, with a 2.5-mm slice thickness at the level of the hips, knees, and ankles in one scan. The patients were scanned in the supine position with the knee fully extended. The exclusion criteria were previous (1) fracture, (2) osteotomy of the femur, or (3) implantation of a total or partial hip or knee arthroplasty. Randomization was performed by including the first 40 cases from the list, after sorting the cases alphabetically in ascending order by last name. With a standardized measurement technique, the parameters described in the following sections were determined. The cases covered a broad variety of different clinical indications (assessment of limb rotation after fracture of the contralateral limb, patellofemoral disorders, and so on). Parameters of Femoral AV In clinical practice total femoral AV (total AV) is determined in the transverse plane between the femoral neck (proximal femur) and the posterior condylar line (distal femur).2,9 In addition, recent research introduced a method that provides additional information on whether the pathologic femoral AV is located more proximally or distally on the femur.10 Accordingly, the following 4 lines were determined from the CT scans: 1 through the center of the femoral head and neck; 1 through the top of the lesser trochanter and the center of the femoral shaft; 1 as a tangent to the dorsal part of the distal femur (for this purpose, we chose the slice just above the point of attachment of the gastrocnemius head); and 1 as a tangent to the posterior condyles. Between the respective lines, the following parameters of femoral AV could be measured: (1) total AV, (2) proximal AV, (3) diaphyseal AV, and (4) distal AV (Fig 1). Parameters of Trochlear Morphology For an exact evaluation, all the trochlea parameters were determined from 2 different axial CT slices, in a manner similar to that suggested by previous research11,12: the proximal slice at the proximal aspect of the trochlea and the distal slice 0.5 cm farther distally. Trochlear morphology was assessed with the semiquantitative Dejour classification.13,14 Besides the dysplastic types A to D, a normal trochlea was designated type 0 (sulcus angle <145 ). Because there was no strong consensus in previous research regarding the reliability of the Dejour classification,15-18 we decided also to use the quantitative trochlea heights as suggested by Biedert and Bachmann.12 The lateral, central, and medial heights of the trochlea were measured in the anteroposterior direction and expressed as a percentage of the width of the distal femur.
Fig 1. Measurement of femoral anteversion of a left femur at 4 levels between the lines shown: (1) line through the center of the femoral head and center of the neck, (2) line through the center of the lesser trochanter and center of the femoral shaft, (3) line dorsal to the distal femur (popliteal surface), and (4) line dorsal to the posterior condyles. Proximal anteversion is calculated between lines 1 and 2, diaphyseal anteversion is calculated between lines 2 and 3, distal anteversion is calculated between lines 3 and 4, and total anteversion is calculated between lines 1 and 4.
The parameter transverse trochlea shift was also determined as previously reported.11 The deepest point of the bony trochlea (or in cases with a convex trochlea, the most prominent point) was marked, and a line was drawn perpendicular to the posterior condyle. The distance between this line and a lateral tangent perpendicular to the posterior condylar line was taken as the transverse trochlea shift and expressed as a percentage of the mediolateral width of the distal femur. Trochlea depth was determined as previously reported.11 The difference between the lateral condylar height and the sulcus height was measured and expressed as a percentage of the lateral condylar height. As suggested by previous researchers,11,19,20 the sulcus angle was defined by the deepest point and the lateral and medial highest points of the trochlea. As shown in previous publications,11,21 the lateral trochlea slope (lateral trochlea inclination) was determined by a tangent to the lateral facet of the trochlea. The angle between this tangent and the posterior condylar line was taken as the lateral trochlea slope (Fig 2). All the aforementioned parameters were always assessed as suggested by the original articles. Because we found good inter-rater reliability for the described torsion measurement on CT in a recent analysis (intraclass correlation coefficient, 0.574 to 0.916; unpublished
RELATION OF FEMORAL ANTEVERSION TO TROCHLEA
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correlated with the sulcus angle (r ¼ 0.408, P ¼ .009). The distal AV showed significant correlations with medial, central, and lateral trochlea height (0.340 < r < 0.434, .005 < P < .032) and with Dejour trochlea type (r ¼ 0.321, P ¼ .043).
Discussion
Fig 2. Measurement of lateral (L), central (C), and medial (M) trochlea height, as well as trochlea shift (TS), and determination of sulcus angle (SA) and lateral trochlea slope (LTS) on an axial computed tomography slice of a left knee. F indicates the total width of the femoral condyle (i.e., 100%).
results, P.W.F. 2015), in this study all measurements were performed by 1 investigator (J.R.). Measurements were always performed with the same software (Impax EE; Agfa HealthCare, Mortsel, Belgium). Statistical Analysis The aforementioned parameters were transferred to an SPSS spreadsheet (SPSS, Chicago, IL). To prove or disprove the aforementioned hypothesis, Pearson correlation analysis was performed between the variables of AV and parameters of trochlear morphology. We defined a as .05.
Results The hospital’s PACS covered CT scans of 560 limbs. A total of 378 cases had to be excluded according to the aforementioned criteria. The descriptive statistics for the femoral AV parameters of the 40 included cases were as follows: total AV, 25.9 9.4 ; proximal AV, 55.1 13.8 ; diaphyseal AV, 37.9 14.8 ; and distal AV, 8.5 3.8 . According to the Dejour classification, 11 patients (27.5%) had no trochlea dysplasia (type 0) whereas 22 patients (55.0%) had type A, 1 patient (2.5%) had type B, and 6 patients (12.5%) had type C. The descriptive statistics for the parameters of AV and trochlear morphology are given in Table 1. The inferential statistics (correlation analysis) confirmed our hypothesis (Table 2). The total AV was significantly correlated with the trochlea parameters trochlea depth (r ¼ 0.340, P ¼ .032), sulcus angle (r ¼ 0.312, P ¼ .05), and lateral trochlea slope (r ¼ 0.494, P ¼ .001). The diaphyseal AV was significantly
The most important finding in this study was that parameters of femoral AV were significantly correlated with parameters of trochlear morphology. Consequently, the study hypothesis was deemed confirmed by the results. The correlations showed that patients with high AV had a more dysplastic femoral trochlea, based on the radiologic parameters evaluated. Diederichs et al.8 already investigated a potential relation between femoral AV and a small selection of parameters of trochlear morphology (lateral trochlea slope, trochlea facet asymmetry, and trochlea depth). In contrast to our study, no such link between AV and trochlea dysplasia was ascertained. Other authors also reported that femoral AV was not related to the sulcus angle, but they did not test other parameters of trochlear morphology.7,22 Wright et al.23 tested relations between femoral AV and, again, a rather small selection of parameters of trochlear morphology (lateral and medial trochlea slope and sulcus angle). They reported a weak correlation between femoral AV and medial trochlea slope. However, the parameters used to assess trochlear morphology in their study might be regarded as insufficient. In particular, parameters determining trochlea dysplasia should be included. As the most established Table 1. Descriptive Statistics for Measurements of Anteversion and Parameters of Trochlear Morphology Mean SD Minimum Maximum AV 25.9 9.4 5.9 48.8 AV total, AV proximal, 55.1 13.8 18.0 85.5 37.9 14.8 76.2 4.1 AV diaphyseal, AV distal, 8.5 3.8 0.6 16.4 Proximal CT slice Medial trochlea height, % 74.4 4.4 61.7 81.6 Central trochlea height, % 70.8 4.4 60.7 77.8 Lateral trochlea height, % 78.6 4.8 62.8 87.0 Transverse trochlea shift, % 47.9 5.5 30.5 59.7 Trochlea depth, 7.8 3.3 0.9 14.4 Sulcus angle, 151.1 9.5 132.5 169.2 Lateral trochlea slope, 15.1 5.7 0.6 27.2 Distal CT slice Medial trochlea height, % 76.1 5.4 54.5 84.6 Central trochlea height, % 69.1 4.7 53.2 76.8 Lateral trochlea height, % 78.8 5.8 56.0 86.9 Transverse trochlea shift, % 47.5 4.3 37.1 57.6 Trochlea depth, 9.7 3.3 1.0 15.7 Sulcus angle, 140.4 11.7 122.3 178.5 Lateral trochlea slope, 19.6 5.4 8.0 33.1 AV, anteversion; CT, computed tomography; SD, standard deviation.
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Table 2. Correlation Coefficients Between Total, Proximal, Diaphyseal, and Distal Anteversion and Parameters of Trochlear Morphology Measured on Proximal Axial CT Slice at Proximal Aspect of Trochlea and Distal Axial CT Slice 0.5 cm Farther Distally r Value Proximal CT slice Medial trochlea height Central trochlea height Lateral trochlea height Transverse trochlea shift Trochlea depth Sulcus angle Sulcus angle categorized Lateral trochlea slope Dejour classification (A-D) Distal CT slice Medial trochlea height Central trochlea height Lateral trochlea height Transverse trochlea shift Trochlea depth Sulcus angle Sulcus angle categorized Lateral trochlea slope Dejour classification (A-D)
Total Anteversion
Proximal Anteversion
Diaphyseal Anteversion
Distal Anteversion
0.051 0.129 0.117 0.155 0.340* 0.302 0.312* 0.494y 0.124
0.143 0.030 0.148 0.006 0.257 0.073 0.092 0.109 0.220
0.240 0.095 0.090 0.078 0.003 0.207 0.252 0.170 0.210
0.357* 0.434y 0.374* 0.008 0.047 0.223 0.129 0.151 0.321*
0.074 0.074 0.127 0.098 0.330* 0.300 0.283 0.437y 0.056
0.088 0.158 0.152 0.016 0.044 0.181 0.214 0.039 0.171
0.110 0.085 0.066 0.040 0.235 0.397y 0.408y 0.234 0.159
0.340* 0.427y 0.375y 0.019 0.049 0.001 0.021 0.048 0.174
CT, computed tomography. *Significant r value at P < .05. y Significant r value at P < .01.
parameters of trochlea dysplasia, the trochlea heights described by Biedert and Bachmann12 and the Dejour dysplasia classification13,14 were included. Despite the limitations of the study conducted by Wright et al., their findings are in principle confirmed and substantially expanded by our study. Regarding the population under investigation, the 2 studies appear to be complementary. Whereas the study by Wright et al. included data from patients who underwent an expanded version of a medically prescribed CT scan of the trunk (to investigate gastrointestinal or urogenital conditions and therefore no complaints concerning the lower limbs), our patients’ CT scans were performed for different kinds of complaints concerning the lower limbs. This is also reflected by the different mean values of total AV in the 2 studies (12.6 in the study by Wright at al.). Other studies did not specifically test for a relation between femoral AV and trochlear morphology but instead tested for relations between AV and patellofemoral tracking or knee pain.24,25 One study reported no relation between patellar lateralization and femoral AV,24 and the other reported a relation between femoral AV and knee pain.25 Our study additionally analyzed femoral AV in 3 stages (proximal, diaphyseal, and distal AV) to relate it to trochlear morphology. This extended analysis was prompted by 2 observations: (1) the work by Seitlinger et al.,10 who described their method of additionally
analyzing femoral AV at 3 levels (as described in the Methods section), and (2) inconsistencies in the literature on whether rotational osteotomies of the femur should be performed at the proximal or distal aspect of the femur.2,26-28 Therefore, this extended analysis aimed to also provide recommendations on the ideal localization of rotational osteotomies in patients with PFJ disorders and pathologic femoral AV. Interestingly, we found significant correlations with trochlea dysplasia only for distal AV and not for proximal AV. These findings could indicate that the distal femur is probably the preferred location for rotational osteotomies. The strengths of the study are that it provides scientific knowledge in a field that was previously investigated only marginally. Compared with the few studies that previously dealt with the same issue,8,23 our study applies a much more comprehensive set of trochlea indices. Limitations The following limitations are acknowledged and might also serve as suggestions for future studies: This was a retrospective study with the weaknesses associated with such studies. We were not able to analyze for parameters other than those described earlier. It would have been interesting to include additional clinical outcome data (e.g., patellofemoral questionnaire). Second, it is acknowledged that the CT scan data were randomly taken from the university hospital’s PACS. Consequently, most of the patients who underwent the
RELATION OF FEMORAL ANTEVERSION TO TROCHLEA
CT scans might have had some kind of lower-limb complaint. Third, with the femoral trochlea, only 1 static factor of the PFJ was investigated, although the PFJ is a much more complex system composed also of passive (retinacula) and active (muscles) soft tissues. Fourth, patients with a previous fracture, osteotomy, or arthroplasty of the hip or knee were excluded from the study. Therefore, patients with potentially significant pathology of the PFJ might have been excluded. These exclusion criteria might be regarded as selection bias.
13. 14.
15.
Conclusions
16.
The morphology of the trochlea is significantly related to femoral AV. Increased AV is associated with a flatter, more dysplastic trochlea. This was particularly true for AV located at the distal femur.
17.
References 1. Biedert RM. Osteotomies. Orthopade 2008;37:872:874876, 878-880 passim [in German]. 2. Bruce WD, Stevens PM. Surgical correction of miserable malalignment syndrome. J Pediatr Orthop 2004;24:392-396. 3. Lee TQ, Anzel SH, Bennett KA, Pang D, Kim WC. The influence of fixed rotational deformities of the femur on the patellofemoral contact pressures in human cadaver knees. Clin Orthop Relat Res 1994;(302):69-74. 4. Mehl J, Feucht MJ, Bode G, Dovi-Akue D, Südkamp NP, Niemeyer P. Association between patellar cartilage defects and patellofemoral geometry: A matched-pair MRI comparison of patients with and without isolated patellar cartilage defects. Knee Surg Sports Traumatol Arthrosc 2016;24:838-846. 5. Koh JL, Stewart C. Patellar instability. Clin Sports Med 2014;33:461-476. 6. Mofidi A, Veravalli K, Jinnah RH, Poehling GG. Association and impact of patellofemoral dysplasia on patellofemoral arthropathy and arthroplasty. Knee 2014;21:509-513. 7. Aks¸ahin E, Güzel A, Erdogan AO, et al. The patellofemoral kinematics in patients with untreated developmental dislocation of the hip suffering from patellofemoral pain. Knee Surg Sports Traumatol Arthrosc 2012;20:2337-2347. 8. Diederichs G, Köhlitz T, Kornaropoulos E, Heller MO, Vollnberg B, Scheffler S. Magnetic resonance imaging analysis of rotational alignment in patients with patellar dislocations. Am J Sports Med 2013;41:51-57. 9. Eckhoff DG, Johnson KK. Three-dimensional computed tomography reconstruction of tibial torsion. Clin Orthop Relat Res 1994;(302):42-46. 10. Seitlinger G, Moroder P, Scheurecker G, Hofmann S, Gerlsamer RP. The contribution of different femur segments to overall femur torsion [published online April 22, 2016]. Am J Sports Med. doi:10.1177/0363546516639945. 11. Fucentese SF, Schöttle PB, Pfirrmann CWA, Romero J. CT changes after trochleoplasty for symptomatic trochlear dysplasia. Knee Surg Sports Traumatol Arthrosc 2007;15: 168-174. 12. Biedert RM, Bachmann M. Anterior-posterior trochlear measurements of normal and dysplastic trochlea by axial
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magnetic resonance imaging. Knee Surg Sports Traumatol Arthrosc 2009;17:1225-1230. Dejour D, Le Coultre B. Osteotomies in patello-femoral instabilities. Sports Med Arthrosc 2007;15:39-46. Dejour D, Saggin P. The sulcus deepening trochleoplastydThe Lyon’s procedure. Int Orthop 2010;34: 311-316. Lippacher S, Dejour D, Elsharkawi M, et al. Observer agreement on the Dejour trochlear dysplasia classification: A comparison of true lateral radiographs and axial magnetic resonance images. Am J Sports Med 2012;40: 837-843. Nelitz M, Lippacher S, Reichel H, Dornacher D. Evaluation of trochlear dysplasia using MRI: Correlation between the classification system of Dejour and objective parameters of trochlear dysplasia. Knee Surg Sports Traumatol Arthrosc 2014;22:120-127. Remy F, Besson A, Migaud H, Cotten A, Gougeon F, Duquennoy A. Reproducibility of the radiographic analysis of dysplasia of the femoral trochlea. Intra- and interobserver analysis of 68 knees. Rev Chir Orthop Reparatrice Appar Mot 1998;84:728-733 [in French]. Rémy F, Chantelot C, Fontaine C, Demondion X, Migaud H, Gougeon F. Inter- and intraobserver reproducibility in radiographic diagnosis and classification of femoral trochlear dysplasia. Surg Radiol Anat 1998;20:285-289. Schutzer SF, Ramsby GR, Fulkerson JP. Computed tomographic classification of patellofemoral pain patients. Orthop Clin North Am 1986;17:235-248. Beaconsfield T, Pintore E, Maffulli N, Petri GJ. Radiological measurements in patellofemoral disorders. A review. Clin Orthop Relat Res 1994;(308):18-28. Carrillon Y, Abidi H, Dejour D, Fantino O, Moyen B, TranMinh VA. Patellar instability: Assessment on MR images by measuring the lateral trochlear inclinationdInitial experience. Radiology 2000;216:582-585. Reikerås O. Patellofemoral characteristics in patients with increased femoral anteversion. Skeletal Radiol 1992;21: 311-313. Wright SJ, Boymans TAEJ, Grimm B, Miles AW, Kessler O. Strong correlation between the morphology of the proximal femur and the geometry of the distal femoral trochlea. Knee Surg Sport Traumatol Arthrosc 2014;22:2900-2910. Abadie P, Galaud B, Michaut M, Fallet L, Boisrenoult P, Beaufils P. Distal femur rotational alignment and patellar subluxation: A CT scan in vivo assessment. Orthop Traumatol Surg Res 2009;95:267-271. Rethlefsen SA, Nguyen DT, Wren TAL, Milewski MD, Kay RM. Knee pain and patellofemoral symptoms in patients with cerebral palsy. J Pediatr Orthop 2015;35: 519-522. Delgado ED, Schoenecker PL, Rich MM, Capelli AM. Treatment of severe torsional malalignment syndrome. J Pediatr Orthop 1996;16:484-488. Dickschas J, Harrer J, Reuter B, Schwitulla J, Strecker W. Torsional osteotomies of the femur. J Orthop Res 2015;33: 318-324. Stevens PM, Gililland JM, Anderson LA, Mickelson JB, Nielson J, Klatt JW. Success of torsional correction surgery after failed surgeries for patellofemoral pain and instability. Strategies Trauma Limb Reconstr 2014;9:5-12.
Purpose: To investigate the possible relation between femoral anteversion (AV) and trochlear morphology. Methods: Among 560 available lower-limb computed tomography (CT) scans, those with previous fracture, arthroplasty, or osteotomy were excluded and 40 cases were randomly selected. The following 4 lines were determined from the CT scans: 1 through the center of the femoral head and neck; 1 through the lesser trochanter and the center of the femoral shaft; 1 as a tangent to the dorsal part of the distal femur, just above the gastrocnemius insertion; and 1 as a tangent to the posterior condyles. Between the respective lines, the following parameters of femoral AV were determined: (1) total AV, (2) proximal AV, (3) diaphyseal AV, and (4) distal AV. Trochlea parameters were determined from 2 separate axial CT slices (proximal trochlea and 5 mm farther distally): trochlea height (medial, central, lateral), transverse trochlea shift, trochlea depth, sulcus angle, lateral trochlea slope, and Dejour trochlea type. To prove or disprove our study hypothesis, a correlation analysis was performed between the variables of AV and trochlear morphology. Results: The total AV was significantly correlated with the trochlea parameters trochlea depth (P ¼ .032), sulcus angle (P ¼ .05), and lateral trochlea slope (P ¼ .001). The diaphyseal AV was significantly correlated with the sulcus angle (P ¼ .009). The distal AV showed significant correlations with medial, central, and lateral trochlea height (.005 < P < .032) and with Dejour trochlea type (P ¼ .043). Conclusions: The morphology of the trochlea is significantly related to femoral AV. Increased AV is associated with a flatter, more dysplastic trochlea. This was particularly true for AV located at the distal femur. Level of Evidence: Level III, diagnostic study of nonconsecutive patients.
n the clinical field of patellofemoral disorders, limb alignment in the transverse plane is a regular topic of discussion. It was reported that many disorders of the patellofemoral joint (PFJ) (patellofemoral pain, patellofemoral instability, and lateral patellofemoral hypercompression) are associated with abnormal femoral anteversion (AV).1-3 In addition, disorders of the PFJ
I
From the Department of Orthopaedic Surgery (M.C.L., P.W.F.), Center of Diagnostic Radiology (T.D.) and Department of Traumatology (R.E.A.), Medical University of Innsbruck, Innsbruck; Medical University of Innsbruck (J.R.), Innsbruck; and Department of Orthopaedic Surgery, Krankenhaus Oberndorf (G.S.), Oberndorf bei Salzburg, Austria. The authors report that they have no conflicts of interest in the authorship and publication of this article. The abstract of this study has been selected as the winner of the ISAKOS (International Society of Arthroscopy, Knee Surgery & Orthopaedic Sports Medicine) Patellofemoral Research Excellence Award 2015. Received July 31, 2015; accepted March 15, 2016. Address correspondence to Peter Wilhelm Ferlic, M.D., Medical University of Innsbruck, Anichstrasse 35, 6020 Innsbruck, Austria. E-mail: peter.ferlic@ gmail.com Ó 2016 by the Arthroscopy Association of North America 0749-8063/15717/$36.00 http://dx.doi.org/10.1016/j.arthro.2016.03.023
are often related to abnormal morphology of the femoral trochlea.4-6 Therefore, it might also be speculated that femoral AV could be directly linked to trochlear morphology. This is because increased femoral AV can be expected to be accompanied by an increased Q angle, which would make greater demands on the lateral facet and fewer demands on the medial facet, thus changing the morphology of the trochlea during growth. However, previous researchers rarely dealt with the relation between femoral AV and trochlear morphology.7,8 Given the insufficient knowledge available in the literature, the purpose of this study was to investigate the possible relation between femoral AV and trochlear morphology. We hypothesized that widely accepted parameters of trochlear morphology would show significant correlations with parameters of femoral AV.
Methods After we obtained the approval of the ethics committee of our medical university, a retrospective analysis was conducted of all lower-limb computed tomography (CT) scans available in our university
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol
-,
No
-
(Month), 2016: pp 1-5
1
2
M. C. LIEBENSTEINER ET AL.
hospital’s picture archiving and communication system (PACS) performed between August 1996 and February 2013. Multislice CT images of lower limbs had been made with a helical scan technique, without contrast media, with a 2.5-mm slice thickness at the level of the hips, knees, and ankles in one scan. The patients were scanned in the supine position with the knee fully extended. The exclusion criteria were previous (1) fracture, (2) osteotomy of the femur, or (3) implantation of a total or partial hip or knee arthroplasty. Randomization was performed by including the first 40 cases from the list, after sorting the cases alphabetically in ascending order by last name. With a standardized measurement technique, the parameters described in the following sections were determined. The cases covered a broad variety of different clinical indications (assessment of limb rotation after fracture of the contralateral limb, patellofemoral disorders, and so on). Parameters of Femoral AV In clinical practice total femoral AV (total AV) is determined in the transverse plane between the femoral neck (proximal femur) and the posterior condylar line (distal femur).2,9 In addition, recent research introduced a method that provides additional information on whether the pathologic femoral AV is located more proximally or distally on the femur.10 Accordingly, the following 4 lines were determined from the CT scans: 1 through the center of the femoral head and neck; 1 through the top of the lesser trochanter and the center of the femoral shaft; 1 as a tangent to the dorsal part of the distal femur (for this purpose, we chose the slice just above the point of attachment of the gastrocnemius head); and 1 as a tangent to the posterior condyles. Between the respective lines, the following parameters of femoral AV could be measured: (1) total AV, (2) proximal AV, (3) diaphyseal AV, and (4) distal AV (Fig 1). Parameters of Trochlear Morphology For an exact evaluation, all the trochlea parameters were determined from 2 different axial CT slices, in a manner similar to that suggested by previous research11,12: the proximal slice at the proximal aspect of the trochlea and the distal slice 0.5 cm farther distally. Trochlear morphology was assessed with the semiquantitative Dejour classification.13,14 Besides the dysplastic types A to D, a normal trochlea was designated type 0 (sulcus angle <145 ). Because there was no strong consensus in previous research regarding the reliability of the Dejour classification,15-18 we decided also to use the quantitative trochlea heights as suggested by Biedert and Bachmann.12 The lateral, central, and medial heights of the trochlea were measured in the anteroposterior direction and expressed as a percentage of the width of the distal femur.
Fig 1. Measurement of femoral anteversion of a left femur at 4 levels between the lines shown: (1) line through the center of the femoral head and center of the neck, (2) line through the center of the lesser trochanter and center of the femoral shaft, (3) line dorsal to the distal femur (popliteal surface), and (4) line dorsal to the posterior condyles. Proximal anteversion is calculated between lines 1 and 2, diaphyseal anteversion is calculated between lines 2 and 3, distal anteversion is calculated between lines 3 and 4, and total anteversion is calculated between lines 1 and 4.
The parameter transverse trochlea shift was also determined as previously reported.11 The deepest point of the bony trochlea (or in cases with a convex trochlea, the most prominent point) was marked, and a line was drawn perpendicular to the posterior condyle. The distance between this line and a lateral tangent perpendicular to the posterior condylar line was taken as the transverse trochlea shift and expressed as a percentage of the mediolateral width of the distal femur. Trochlea depth was determined as previously reported.11 The difference between the lateral condylar height and the sulcus height was measured and expressed as a percentage of the lateral condylar height. As suggested by previous researchers,11,19,20 the sulcus angle was defined by the deepest point and the lateral and medial highest points of the trochlea. As shown in previous publications,11,21 the lateral trochlea slope (lateral trochlea inclination) was determined by a tangent to the lateral facet of the trochlea. The angle between this tangent and the posterior condylar line was taken as the lateral trochlea slope (Fig 2). All the aforementioned parameters were always assessed as suggested by the original articles. Because we found good inter-rater reliability for the described torsion measurement on CT in a recent analysis (intraclass correlation coefficient, 0.574 to 0.916; unpublished
RELATION OF FEMORAL ANTEVERSION TO TROCHLEA
3
correlated with the sulcus angle (r ¼ 0.408, P ¼ .009). The distal AV showed significant correlations with medial, central, and lateral trochlea height (0.340 < r < 0.434, .005 < P < .032) and with Dejour trochlea type (r ¼ 0.321, P ¼ .043).
Discussion
Fig 2. Measurement of lateral (L), central (C), and medial (M) trochlea height, as well as trochlea shift (TS), and determination of sulcus angle (SA) and lateral trochlea slope (LTS) on an axial computed tomography slice of a left knee. F indicates the total width of the femoral condyle (i.e., 100%).
results, P.W.F. 2015), in this study all measurements were performed by 1 investigator (J.R.). Measurements were always performed with the same software (Impax EE; Agfa HealthCare, Mortsel, Belgium). Statistical Analysis The aforementioned parameters were transferred to an SPSS spreadsheet (SPSS, Chicago, IL). To prove or disprove the aforementioned hypothesis, Pearson correlation analysis was performed between the variables of AV and parameters of trochlear morphology. We defined a as .05.
Results The hospital’s PACS covered CT scans of 560 limbs. A total of 378 cases had to be excluded according to the aforementioned criteria. The descriptive statistics for the femoral AV parameters of the 40 included cases were as follows: total AV, 25.9 9.4 ; proximal AV, 55.1 13.8 ; diaphyseal AV, 37.9 14.8 ; and distal AV, 8.5 3.8 . According to the Dejour classification, 11 patients (27.5%) had no trochlea dysplasia (type 0) whereas 22 patients (55.0%) had type A, 1 patient (2.5%) had type B, and 6 patients (12.5%) had type C. The descriptive statistics for the parameters of AV and trochlear morphology are given in Table 1. The inferential statistics (correlation analysis) confirmed our hypothesis (Table 2). The total AV was significantly correlated with the trochlea parameters trochlea depth (r ¼ 0.340, P ¼ .032), sulcus angle (r ¼ 0.312, P ¼ .05), and lateral trochlea slope (r ¼ 0.494, P ¼ .001). The diaphyseal AV was significantly
The most important finding in this study was that parameters of femoral AV were significantly correlated with parameters of trochlear morphology. Consequently, the study hypothesis was deemed confirmed by the results. The correlations showed that patients with high AV had a more dysplastic femoral trochlea, based on the radiologic parameters evaluated. Diederichs et al.8 already investigated a potential relation between femoral AV and a small selection of parameters of trochlear morphology (lateral trochlea slope, trochlea facet asymmetry, and trochlea depth). In contrast to our study, no such link between AV and trochlea dysplasia was ascertained. Other authors also reported that femoral AV was not related to the sulcus angle, but they did not test other parameters of trochlear morphology.7,22 Wright et al.23 tested relations between femoral AV and, again, a rather small selection of parameters of trochlear morphology (lateral and medial trochlea slope and sulcus angle). They reported a weak correlation between femoral AV and medial trochlea slope. However, the parameters used to assess trochlear morphology in their study might be regarded as insufficient. In particular, parameters determining trochlea dysplasia should be included. As the most established Table 1. Descriptive Statistics for Measurements of Anteversion and Parameters of Trochlear Morphology Mean SD Minimum Maximum AV 25.9 9.4 5.9 48.8 AV total, AV proximal, 55.1 13.8 18.0 85.5 37.9 14.8 76.2 4.1 AV diaphyseal, AV distal, 8.5 3.8 0.6 16.4 Proximal CT slice Medial trochlea height, % 74.4 4.4 61.7 81.6 Central trochlea height, % 70.8 4.4 60.7 77.8 Lateral trochlea height, % 78.6 4.8 62.8 87.0 Transverse trochlea shift, % 47.9 5.5 30.5 59.7 Trochlea depth, 7.8 3.3 0.9 14.4 Sulcus angle, 151.1 9.5 132.5 169.2 Lateral trochlea slope, 15.1 5.7 0.6 27.2 Distal CT slice Medial trochlea height, % 76.1 5.4 54.5 84.6 Central trochlea height, % 69.1 4.7 53.2 76.8 Lateral trochlea height, % 78.8 5.8 56.0 86.9 Transverse trochlea shift, % 47.5 4.3 37.1 57.6 Trochlea depth, 9.7 3.3 1.0 15.7 Sulcus angle, 140.4 11.7 122.3 178.5 Lateral trochlea slope, 19.6 5.4 8.0 33.1 AV, anteversion; CT, computed tomography; SD, standard deviation.
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M. C. LIEBENSTEINER ET AL.
Table 2. Correlation Coefficients Between Total, Proximal, Diaphyseal, and Distal Anteversion and Parameters of Trochlear Morphology Measured on Proximal Axial CT Slice at Proximal Aspect of Trochlea and Distal Axial CT Slice 0.5 cm Farther Distally r Value Proximal CT slice Medial trochlea height Central trochlea height Lateral trochlea height Transverse trochlea shift Trochlea depth Sulcus angle Sulcus angle categorized Lateral trochlea slope Dejour classification (A-D) Distal CT slice Medial trochlea height Central trochlea height Lateral trochlea height Transverse trochlea shift Trochlea depth Sulcus angle Sulcus angle categorized Lateral trochlea slope Dejour classification (A-D)
Total Anteversion
Proximal Anteversion
Diaphyseal Anteversion
Distal Anteversion
0.051 0.129 0.117 0.155 0.340* 0.302 0.312* 0.494y 0.124
0.143 0.030 0.148 0.006 0.257 0.073 0.092 0.109 0.220
0.240 0.095 0.090 0.078 0.003 0.207 0.252 0.170 0.210
0.357* 0.434y 0.374* 0.008 0.047 0.223 0.129 0.151 0.321*
0.074 0.074 0.127 0.098 0.330* 0.300 0.283 0.437y 0.056
0.088 0.158 0.152 0.016 0.044 0.181 0.214 0.039 0.171
0.110 0.085 0.066 0.040 0.235 0.397y 0.408y 0.234 0.159
0.340* 0.427y 0.375y 0.019 0.049 0.001 0.021 0.048 0.174
CT, computed tomography. *Significant r value at P < .05. y Significant r value at P < .01.
parameters of trochlea dysplasia, the trochlea heights described by Biedert and Bachmann12 and the Dejour dysplasia classification13,14 were included. Despite the limitations of the study conducted by Wright et al., their findings are in principle confirmed and substantially expanded by our study. Regarding the population under investigation, the 2 studies appear to be complementary. Whereas the study by Wright et al. included data from patients who underwent an expanded version of a medically prescribed CT scan of the trunk (to investigate gastrointestinal or urogenital conditions and therefore no complaints concerning the lower limbs), our patients’ CT scans were performed for different kinds of complaints concerning the lower limbs. This is also reflected by the different mean values of total AV in the 2 studies (12.6 in the study by Wright at al.). Other studies did not specifically test for a relation between femoral AV and trochlear morphology but instead tested for relations between AV and patellofemoral tracking or knee pain.24,25 One study reported no relation between patellar lateralization and femoral AV,24 and the other reported a relation between femoral AV and knee pain.25 Our study additionally analyzed femoral AV in 3 stages (proximal, diaphyseal, and distal AV) to relate it to trochlear morphology. This extended analysis was prompted by 2 observations: (1) the work by Seitlinger et al.,10 who described their method of additionally
analyzing femoral AV at 3 levels (as described in the Methods section), and (2) inconsistencies in the literature on whether rotational osteotomies of the femur should be performed at the proximal or distal aspect of the femur.2,26-28 Therefore, this extended analysis aimed to also provide recommendations on the ideal localization of rotational osteotomies in patients with PFJ disorders and pathologic femoral AV. Interestingly, we found significant correlations with trochlea dysplasia only for distal AV and not for proximal AV. These findings could indicate that the distal femur is probably the preferred location for rotational osteotomies. The strengths of the study are that it provides scientific knowledge in a field that was previously investigated only marginally. Compared with the few studies that previously dealt with the same issue,8,23 our study applies a much more comprehensive set of trochlea indices. Limitations The following limitations are acknowledged and might also serve as suggestions for future studies: This was a retrospective study with the weaknesses associated with such studies. We were not able to analyze for parameters other than those described earlier. It would have been interesting to include additional clinical outcome data (e.g., patellofemoral questionnaire). Second, it is acknowledged that the CT scan data were randomly taken from the university hospital’s PACS. Consequently, most of the patients who underwent the
RELATION OF FEMORAL ANTEVERSION TO TROCHLEA
CT scans might have had some kind of lower-limb complaint. Third, with the femoral trochlea, only 1 static factor of the PFJ was investigated, although the PFJ is a much more complex system composed also of passive (retinacula) and active (muscles) soft tissues. Fourth, patients with a previous fracture, osteotomy, or arthroplasty of the hip or knee were excluded from the study. Therefore, patients with potentially significant pathology of the PFJ might have been excluded. These exclusion criteria might be regarded as selection bias.
13. 14.
15.
Conclusions
16.
The morphology of the trochlea is significantly related to femoral AV. Increased AV is associated with a flatter, more dysplastic trochlea. This was particularly true for AV located at the distal femur.
17.
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