- Email: [email protected]
A Proposed Classification of Supracondylar Femur Fractures Above Total Knee Arthroplasties
The Journal of Arthroplasty Vol. 21 No. 3 2006
A Proposed Classification of Supracondylar Femur Fractures Above Total Knee Arthroplasties Edward T. Su, MD, Erik N. Kubiak, MD, Hargovind DeWal, MD, Rudi Hiebert, BS, and Paul E. Di Cesare, MD
Abstract: A new classification system is proposed for supracondylar femur fractures above total knee arthroplasties based on fracture location relative to the femoral component. Radiographs of 28 cases were evaluated and classified according to the proposed system by 12 physicians: 3 trauma specialists, 3 adult reconstruction specialists, 3 musculoskeletal radiologists, and 3 orthopaedic residents. The same 12 physicians reevaluated the same 28 cases 3 months later. The mean reliability coefficient for all observers was 0.74 (substantial agreement). The coefficient for reproducibility after 3 months was 0.85 (almost perfect). The power of the study was 80%. The proposed classification system is easy to use and has good interobserver reliability among orthopaedic residents, orthopaedic attendings—trauma and reconstruction—and radiologists. Intraobserver reliability was also excellent at 3 months. Key words: periprosthetic, femur, fracture, total knee arthroplasty, radiographs, classification. n 2006 Elsevier Inc. All rights reserved.
There are several interpretations of what constitutes bthe supracondylar region of the distal femur.Q Neer et al [6] in 1967 defined it as the lower 3 in (7.62 cm) of the femur (see Table 1). Culp et al [4] specified 9 cm proximal to the knee joint line as the cutoff point [7]. Sisto et al [2] included fractures occurring within 15 cm proximal to the knee joint line. For the purposes of this paper, we define a supracondylar periprosthetic fracture as one occurring within 15 cm of the joint line or, in the case of a stemmed component, less than 5 cm from the proximal end of the femur. Treatment of supracondylar periprosthetic fractures includes both nonoperative means (skeletal traction, bracing) and surgery (external fixation, open or closed reduction with internal fixation, revision arthroplasty with or without distal femoral allografts). Supracondylar periprosthetic fracture classification systems—for example, those devised by DiGioia and Rubash [8], Chen et al [5], and Rorabeck and Taylor [9,10] (see Tables 2-4)— are helpful for distinguishing fractures amenable to
Supracondylar periprosthetic femur fractures above total knee arthroplasties are an uncommon complication after total knee arthroplasty, with a reported incidence of 0.3% to 2.5% [1-3]. These fractures are most common in elderly patients with osteoporosis and such other risk factors as rheumatoid arthritis, neurological disorders, chronic steroid therapy, femoral anterior cortical notching, and revision knee arthroplasty [1,4,5]. The usual mechanism of injury is a fall directly onto the flexed knee.
From the Department of Orthopaedic Surgery, Musculoskeletal Research Center, NYU-Hospital for Joint Diseases Orthopaedic Institute, New York, New York. Submitted June 30, 2003; accepted May 15, 2005. No benefits or funds were received in support of the study. Reprint requests: Paul E. Di Cesare, MD, Department of Orthopaedic Surgery, Musculoskeletal Research Center, NYUHospital for Joint Diseases Orthopaedic Institute, 301 East 17th Street, Room 1501, New York, NY 10003. n 2006 Elsevier Inc. All rights reserved. 0883-5403/06/1906-0004$32.00/0 doi:10.1016/j.arth.2005.05.022
405
406 The Journal of Arthroplasty Vol. 21 No. 3 April 2006 Table 1. Neer et al [6] Classification Type I Type II A B Type III
Undisplaced (b5 mm displacement and/or b58 angulation) Displaced N1 cm With medial femoral shaft displacement With internal femoral shaft displacement Displaced and comminuted
nonoperative treatment from those requiring surgery; they do not, however, distinguish among operative treatments. Surgical repair for these fractures has become more common as the need to mobilize patients soon after injury to limit morbidity and mortality has become better recognized. Several operative treatments have been used to stabilize these special fractures, including but not limited to intramedullary nails placed both retrograde and antegrade, buttress plates, fixed-angle plates, and external fixators. Selection of the appropriate device relies heavily upon the location of the fracture relative to the total knee component. This crucial point is missed by current classification schemes. For a classification system to be useful, it must be reliable and reproducible, facilitate interaction among medical professionals, and aid in improving conclusions that can be drawn from research. We have created a new classification system for periprosthetic femur fractures that should act as a guide for the treatment of these fractures. The supracondylar periprosthetic femur fracture classification proposed herein is straightforward, consisting of 3 types based on the location of the fracture relative to the femoral component (see Fig. 1) as determined from standard anteroposterior and lateral radiographs.
Materials and Methods Twelve observers were recruited, 3 each of fellowship-trained trauma specialists, fellowshiptrained adult reconstruction specialists, fellow-
Table 2. DiGioia and Rubash [8] Classification Group I Group II Group III
Extra-articular, undisplaced (b5 mm displacement or b58 angulation) Extra-articular, displaced (N5 mm displacement or N58 angulation) Severely displaced (loss of cortical contact) or angulated (N108); may have intercondylar or T-shaped component
Table 3. Chen et al [5] Classification Type I Type II
Nondisplaced (Neer type II) Displaced and/or comminuted (Neer types II and III)
ship-trained musculoskeletal radiologists, and orthopaedic residents. Initially, observers classified 28 consecutive cases of periprosthetic femur fractures above total knee arthroplasties from good-quality anteroposterior and lateral radiographs collected by the first author (ES, who was not among the observers; cases were excluded in which the knee component was stemmed or had an intercondylar box) according to the new classification system outlined in Fig. 1. Cases were identified from our emergency room logs from 1996 to 2002. Subsequently, the observers were shown the same 28 radiographs in random order 3 months later. Observers were not initially informed that they were to be retested, and radiographs were made unavailable for review during the 3-month interval. No time limit was allotted for review of the radiographs. No questions were allowed while the radiographs were being reviewed or during the interval between reviewing sessions. Statistical Analysis Study results were analyzed using the j statistic according to standard criteria described by Landis and Koch [11], where 0.00 to 0.20 = slight agreement, 0.21 to 0.40 = fair agreement, 0.41 to 0.60 = moderate agreement, 0.61 to 0.80 = substantial agreement, and 0.81 to 1.00 = almost perfect agreement. Power analysis of the results was performed for evaluation of intraclass correlation coefficients [12].
Results Interobserver Reliability There was perfect agreement among the 4 observer groups for 61% of the fractures (Table 5). The mean reliability coefficient (j statistic) for orthopaedic trauma specialists was 0.85 (almost perfect
Table 4. Rorabeck and Taylor [10] Classification Type I Type II Type III
Undisplaced fracture; prosthesis intact Displaced fracture; prosthesis intact Displaced or undisplaced fracture; prosthesis loose or failing
Periprosthetic Femur Classification ! Su et al 407
Fig. 1. The 3 types of fracture in the proposed classification system: type I: fracture proximal to the femoral component; type II: fracture originating at the proximal end of femoral component and extending proximally; type III: fracture in which any part of the fracture line can be seen distal to the upper edge of the anterior flange of the femoral component.
agreement); for the adult reconstruction specialists, 0.73 (substantial agreement); for the musculoskeletal radiologists, 0.64 (substantial agreement); and for the residents, 0.80 (substantial agreement). Overall, the mean reliability coefficient for all observers was 0.74 (substantial agreement).
Discussion
Intraobserver Reproducibility At the second assessment 3 months later, intraclass correlation between the first and second review was 0.85 with a lower 95% confidence limit of 0.78 for all physicians combined (Table 6). The mean reliability coefficient (j statistic) for the orthopaedic trauma specialists was 0.91 (almost perfect); for the adult reconstruction specialists, 0.80 (substantial agreement); for the musculoskeletal radiologists, 0.82 (almost perfect agreement); and for the residents, 0.88 (almost perfect agreement). Power Analysis Twenty-eight samples reviewed by 12 physicians had 80% statistical power to demonstrate that the observed intraclass correlation coefficient of 0.74 was statistically distinguishable from an intraclass Table 5. Interrater Correlation Coefficients
All observers Trauma specialists Adult reconstruction specialists Musculoskeletal radiologists Orthopaedic residents
correlation coefficient of 0.59. The intraclass correlation coefficient of 0.74 was statistically significantly greater than a lower boundary of 0.59 that by convention is approximately the demarcation from bmoderateQ to bsubstantialQ reliability [7].
Estimated Correlation
Lower 95% Confidence Limit
0.74 0.85 0.73
0.65 0.76 0.58
0.64 0.80
0.47 0.69
A useful classification system must facilitate communication, education, research, and treatment. To these ends, the ideal classification system would ensure both reliable reproduction of evaluations among observers and reproducible evaluations of a single observer. This is particularly true in orthopaedics for fracture patterns that are seen infrequently and for which there is limited shared experience among treating physicians. Classification systems can guide operative treatment, allowing surgeons to effectively pool cases and discuss appropriate treatment options for specific situations. A reliably reproducible classification scheme facilitates research by allowing treatment methods to be appropriately compared. The proposed classification scheme guides
Table 6. Intraclass Correlation Coefficients (After Repeat Review at 3 Months)
All observers Trauma specialists Adult reconstruction specialists Musculoskeletal radiologists Orthopaedic residents
Estimated Correlation
Lower 95% Confidence Limit
0.85 0.91 0.80
0.78 0.86 0.65
0.82 0.88
0.72 0.81
408 The Journal of Arthroplasty Vol. 21 No. 3 April 2006 the surgeon’s operative treatment choice with a high degree of interobserver reliability and intraobserver reproducibility, thus greatly improving communication among health care specialists. In our opinion, fracture location in relation to the femoral knee component is the best determinant of appropriate operative treatment. Although intramedullary nails have become increasingly popular for the treatment of these fractures, they are not always appropriate. In the authors’ experience, type I fractures are usually most amenable to treatment with an antegrade or retrograde intramedullary nail (if the femoral component has an open box to facilitate nail placement). We do not recommend using metal cutting tools to make a hole in a closed box to facilitate the use of an intramedullary nail as the resultant metal particles may contribute to third body wear. Type II fractures will likely require treatment with either a fixed-angle device or retrograde supracondylar nail (only if the femoral box is open). Type III fractures may be treated by either a fixed-angle device (if the segment of bone remaining can accommodate fixation) or revision arthroplasty with a stemmed femoral component, possibly in combination with a distal femoral allograft. If there is loosening of the femoral component, revision arthroplasty with a stemmed femoral component may be required, regardless of the location of the fracture; however, some surgeons might favor treatment of the fracture first, with later revision of the components. The proposed classification system is easy to use and has good interobserver reliability and intraobserver reproducibility. Application of the proposed classification system toward appropriate surgical management must await careful scrutiny of clinical results; this system is in use at our institution and has proven helpful for guiding treatment for periprosthetic fractures above total knee components and may help investigators compare results with different fracture
treatments to determine optimum fracture therapy in the future.
References 1. Merkel KD, Johnson Jr EW. Supracondylar fracture of the femur after total knee arthroplasty. J Bone Joint Surg Am 1986;68:29. 2. Sisto DJ, et al. Treatment of supracondylar fractures following prosthetic arthroplasty of the knee. Clin Orthop 1985;265. 3. Ritter MA, et al. Anterior femoral notching and ipsilateral supracondylar femur fracture in total knee arthroplasty. J Arthroplasty 1988;3:185. 4. Culp RW, et al. Supracondylar fracture of the femur following prosthetic knee arthroplasty. Clin Orthop 1987;212. 5. Chen F, et al. Management of ipsilateral supracondylar femur fractures following total knee arthroplasty. J Arthroplasty 1994;9:521. 6. Neer CS, Grantham SA, Shelton ML. Treatment of supracondylar fractures following prosthetic arthroplasty of the knee. A study of one hundred and ten cases. J Bone Joint Surg Am 1967;49:591. 7. Cain PR, et al. Periprosthetic femoral fractures following total knee arthroplasty. Clin Orthop 1986;205. 8. DiGioia III AM, Rubash HE. Periprosthetic fractures of the femur after total knee arthroplasty. A literature review and treatment algorithm. Clin Orthop 1991;135. 9. Rorabeck CH, Taylor JW. Periprosthetic fractures of the femur complicating total knee arthroplasty. Orthop Clin North Am 1999;30:265. 10. Rorabeck CH, Taylor JW. Classification of periprosthetic fractures complicating total knee arthroplasty. Orthop Clin North Am 1999;30:209. 11. Landis JR, Koch G. The measurement of observer agreement for categorical data. Biometrics 1977; 33:159. 12. Figgie MP, et al. The results of treatment of supracondylar fracture above total knee arthroplasty. J Arthroplasty 1990;5:267.
A Proposed Classification of Supracondylar Femur Fractures Above Total Knee Arthroplasties Edward T. Su, MD, Erik N. Kubiak, MD, Hargovind DeWal, MD, Rudi Hiebert, BS, and Paul E. Di Cesare, MD
Abstract: A new classification system is proposed for supracondylar femur fractures above total knee arthroplasties based on fracture location relative to the femoral component. Radiographs of 28 cases were evaluated and classified according to the proposed system by 12 physicians: 3 trauma specialists, 3 adult reconstruction specialists, 3 musculoskeletal radiologists, and 3 orthopaedic residents. The same 12 physicians reevaluated the same 28 cases 3 months later. The mean reliability coefficient for all observers was 0.74 (substantial agreement). The coefficient for reproducibility after 3 months was 0.85 (almost perfect). The power of the study was 80%. The proposed classification system is easy to use and has good interobserver reliability among orthopaedic residents, orthopaedic attendings—trauma and reconstruction—and radiologists. Intraobserver reliability was also excellent at 3 months. Key words: periprosthetic, femur, fracture, total knee arthroplasty, radiographs, classification. n 2006 Elsevier Inc. All rights reserved.
There are several interpretations of what constitutes bthe supracondylar region of the distal femur.Q Neer et al [6] in 1967 defined it as the lower 3 in (7.62 cm) of the femur (see Table 1). Culp et al [4] specified 9 cm proximal to the knee joint line as the cutoff point [7]. Sisto et al [2] included fractures occurring within 15 cm proximal to the knee joint line. For the purposes of this paper, we define a supracondylar periprosthetic fracture as one occurring within 15 cm of the joint line or, in the case of a stemmed component, less than 5 cm from the proximal end of the femur. Treatment of supracondylar periprosthetic fractures includes both nonoperative means (skeletal traction, bracing) and surgery (external fixation, open or closed reduction with internal fixation, revision arthroplasty with or without distal femoral allografts). Supracondylar periprosthetic fracture classification systems—for example, those devised by DiGioia and Rubash [8], Chen et al [5], and Rorabeck and Taylor [9,10] (see Tables 2-4)— are helpful for distinguishing fractures amenable to
Supracondylar periprosthetic femur fractures above total knee arthroplasties are an uncommon complication after total knee arthroplasty, with a reported incidence of 0.3% to 2.5% [1-3]. These fractures are most common in elderly patients with osteoporosis and such other risk factors as rheumatoid arthritis, neurological disorders, chronic steroid therapy, femoral anterior cortical notching, and revision knee arthroplasty [1,4,5]. The usual mechanism of injury is a fall directly onto the flexed knee.
From the Department of Orthopaedic Surgery, Musculoskeletal Research Center, NYU-Hospital for Joint Diseases Orthopaedic Institute, New York, New York. Submitted June 30, 2003; accepted May 15, 2005. No benefits or funds were received in support of the study. Reprint requests: Paul E. Di Cesare, MD, Department of Orthopaedic Surgery, Musculoskeletal Research Center, NYUHospital for Joint Diseases Orthopaedic Institute, 301 East 17th Street, Room 1501, New York, NY 10003. n 2006 Elsevier Inc. All rights reserved. 0883-5403/06/1906-0004$32.00/0 doi:10.1016/j.arth.2005.05.022
405
406 The Journal of Arthroplasty Vol. 21 No. 3 April 2006 Table 1. Neer et al [6] Classification Type I Type II A B Type III
Undisplaced (b5 mm displacement and/or b58 angulation) Displaced N1 cm With medial femoral shaft displacement With internal femoral shaft displacement Displaced and comminuted
nonoperative treatment from those requiring surgery; they do not, however, distinguish among operative treatments. Surgical repair for these fractures has become more common as the need to mobilize patients soon after injury to limit morbidity and mortality has become better recognized. Several operative treatments have been used to stabilize these special fractures, including but not limited to intramedullary nails placed both retrograde and antegrade, buttress plates, fixed-angle plates, and external fixators. Selection of the appropriate device relies heavily upon the location of the fracture relative to the total knee component. This crucial point is missed by current classification schemes. For a classification system to be useful, it must be reliable and reproducible, facilitate interaction among medical professionals, and aid in improving conclusions that can be drawn from research. We have created a new classification system for periprosthetic femur fractures that should act as a guide for the treatment of these fractures. The supracondylar periprosthetic femur fracture classification proposed herein is straightforward, consisting of 3 types based on the location of the fracture relative to the femoral component (see Fig. 1) as determined from standard anteroposterior and lateral radiographs.
Materials and Methods Twelve observers were recruited, 3 each of fellowship-trained trauma specialists, fellowshiptrained adult reconstruction specialists, fellow-
Table 2. DiGioia and Rubash [8] Classification Group I Group II Group III
Extra-articular, undisplaced (b5 mm displacement or b58 angulation) Extra-articular, displaced (N5 mm displacement or N58 angulation) Severely displaced (loss of cortical contact) or angulated (N108); may have intercondylar or T-shaped component
Table 3. Chen et al [5] Classification Type I Type II
Nondisplaced (Neer type II) Displaced and/or comminuted (Neer types II and III)
ship-trained musculoskeletal radiologists, and orthopaedic residents. Initially, observers classified 28 consecutive cases of periprosthetic femur fractures above total knee arthroplasties from good-quality anteroposterior and lateral radiographs collected by the first author (ES, who was not among the observers; cases were excluded in which the knee component was stemmed or had an intercondylar box) according to the new classification system outlined in Fig. 1. Cases were identified from our emergency room logs from 1996 to 2002. Subsequently, the observers were shown the same 28 radiographs in random order 3 months later. Observers were not initially informed that they were to be retested, and radiographs were made unavailable for review during the 3-month interval. No time limit was allotted for review of the radiographs. No questions were allowed while the radiographs were being reviewed or during the interval between reviewing sessions. Statistical Analysis Study results were analyzed using the j statistic according to standard criteria described by Landis and Koch [11], where 0.00 to 0.20 = slight agreement, 0.21 to 0.40 = fair agreement, 0.41 to 0.60 = moderate agreement, 0.61 to 0.80 = substantial agreement, and 0.81 to 1.00 = almost perfect agreement. Power analysis of the results was performed for evaluation of intraclass correlation coefficients [12].
Results Interobserver Reliability There was perfect agreement among the 4 observer groups for 61% of the fractures (Table 5). The mean reliability coefficient (j statistic) for orthopaedic trauma specialists was 0.85 (almost perfect
Table 4. Rorabeck and Taylor [10] Classification Type I Type II Type III
Undisplaced fracture; prosthesis intact Displaced fracture; prosthesis intact Displaced or undisplaced fracture; prosthesis loose or failing
Periprosthetic Femur Classification ! Su et al 407
Fig. 1. The 3 types of fracture in the proposed classification system: type I: fracture proximal to the femoral component; type II: fracture originating at the proximal end of femoral component and extending proximally; type III: fracture in which any part of the fracture line can be seen distal to the upper edge of the anterior flange of the femoral component.
agreement); for the adult reconstruction specialists, 0.73 (substantial agreement); for the musculoskeletal radiologists, 0.64 (substantial agreement); and for the residents, 0.80 (substantial agreement). Overall, the mean reliability coefficient for all observers was 0.74 (substantial agreement).
Discussion
Intraobserver Reproducibility At the second assessment 3 months later, intraclass correlation between the first and second review was 0.85 with a lower 95% confidence limit of 0.78 for all physicians combined (Table 6). The mean reliability coefficient (j statistic) for the orthopaedic trauma specialists was 0.91 (almost perfect); for the adult reconstruction specialists, 0.80 (substantial agreement); for the musculoskeletal radiologists, 0.82 (almost perfect agreement); and for the residents, 0.88 (almost perfect agreement). Power Analysis Twenty-eight samples reviewed by 12 physicians had 80% statistical power to demonstrate that the observed intraclass correlation coefficient of 0.74 was statistically distinguishable from an intraclass Table 5. Interrater Correlation Coefficients
All observers Trauma specialists Adult reconstruction specialists Musculoskeletal radiologists Orthopaedic residents
correlation coefficient of 0.59. The intraclass correlation coefficient of 0.74 was statistically significantly greater than a lower boundary of 0.59 that by convention is approximately the demarcation from bmoderateQ to bsubstantialQ reliability [7].
Estimated Correlation
Lower 95% Confidence Limit
0.74 0.85 0.73
0.65 0.76 0.58
0.64 0.80
0.47 0.69
A useful classification system must facilitate communication, education, research, and treatment. To these ends, the ideal classification system would ensure both reliable reproduction of evaluations among observers and reproducible evaluations of a single observer. This is particularly true in orthopaedics for fracture patterns that are seen infrequently and for which there is limited shared experience among treating physicians. Classification systems can guide operative treatment, allowing surgeons to effectively pool cases and discuss appropriate treatment options for specific situations. A reliably reproducible classification scheme facilitates research by allowing treatment methods to be appropriately compared. The proposed classification scheme guides
Table 6. Intraclass Correlation Coefficients (After Repeat Review at 3 Months)
All observers Trauma specialists Adult reconstruction specialists Musculoskeletal radiologists Orthopaedic residents
Estimated Correlation
Lower 95% Confidence Limit
0.85 0.91 0.80
0.78 0.86 0.65
0.82 0.88
0.72 0.81
408 The Journal of Arthroplasty Vol. 21 No. 3 April 2006 the surgeon’s operative treatment choice with a high degree of interobserver reliability and intraobserver reproducibility, thus greatly improving communication among health care specialists. In our opinion, fracture location in relation to the femoral knee component is the best determinant of appropriate operative treatment. Although intramedullary nails have become increasingly popular for the treatment of these fractures, they are not always appropriate. In the authors’ experience, type I fractures are usually most amenable to treatment with an antegrade or retrograde intramedullary nail (if the femoral component has an open box to facilitate nail placement). We do not recommend using metal cutting tools to make a hole in a closed box to facilitate the use of an intramedullary nail as the resultant metal particles may contribute to third body wear. Type II fractures will likely require treatment with either a fixed-angle device or retrograde supracondylar nail (only if the femoral box is open). Type III fractures may be treated by either a fixed-angle device (if the segment of bone remaining can accommodate fixation) or revision arthroplasty with a stemmed femoral component, possibly in combination with a distal femoral allograft. If there is loosening of the femoral component, revision arthroplasty with a stemmed femoral component may be required, regardless of the location of the fracture; however, some surgeons might favor treatment of the fracture first, with later revision of the components. The proposed classification system is easy to use and has good interobserver reliability and intraobserver reproducibility. Application of the proposed classification system toward appropriate surgical management must await careful scrutiny of clinical results; this system is in use at our institution and has proven helpful for guiding treatment for periprosthetic fractures above total knee components and may help investigators compare results with different fracture
treatments to determine optimum fracture therapy in the future.
References 1. Merkel KD, Johnson Jr EW. Supracondylar fracture of the femur after total knee arthroplasty. J Bone Joint Surg Am 1986;68:29. 2. Sisto DJ, et al. Treatment of supracondylar fractures following prosthetic arthroplasty of the knee. Clin Orthop 1985;265. 3. Ritter MA, et al. Anterior femoral notching and ipsilateral supracondylar femur fracture in total knee arthroplasty. J Arthroplasty 1988;3:185. 4. Culp RW, et al. Supracondylar fracture of the femur following prosthetic knee arthroplasty. Clin Orthop 1987;212. 5. Chen F, et al. Management of ipsilateral supracondylar femur fractures following total knee arthroplasty. J Arthroplasty 1994;9:521. 6. Neer CS, Grantham SA, Shelton ML. Treatment of supracondylar fractures following prosthetic arthroplasty of the knee. A study of one hundred and ten cases. J Bone Joint Surg Am 1967;49:591. 7. Cain PR, et al. Periprosthetic femoral fractures following total knee arthroplasty. Clin Orthop 1986;205. 8. DiGioia III AM, Rubash HE. Periprosthetic fractures of the femur after total knee arthroplasty. A literature review and treatment algorithm. Clin Orthop 1991;135. 9. Rorabeck CH, Taylor JW. Periprosthetic fractures of the femur complicating total knee arthroplasty. Orthop Clin North Am 1999;30:265. 10. Rorabeck CH, Taylor JW. Classification of periprosthetic fractures complicating total knee arthroplasty. Orthop Clin North Am 1999;30:209. 11. Landis JR, Koch G. The measurement of observer agreement for categorical data. Biometrics 1977; 33:159. 12. Figgie MP, et al. The results of treatment of supracondylar fracture above total knee arthroplasty. J Arthroplasty 1990;5:267.