JBJS | Interobserver Reliability and Intraobserver Reproducibility of the Modified Ficat Classification System of Osteonecrosis of the Femoral Head*

The Journal of Bone & Joint Surgery, Volume 78, Issue 11

Articles | November 01, 1996

Interobserver Reliability and Intraobserver Reproducibility of the Modified Ficat Classification System of Osteonecrosis of the Femoral Head*

STEPHEN W. SMITH, M.D.†; RALPH A. MEYER, PH.D.‡; PATRICK M. CONNOR, M.D.§; STUART E. SMITH, M.D.¶; EDWARD N. HANLEY, JR., M.D.‡, CHARLOTTE, NORTH CAROLINA

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Investigation performed at the Department of Orthopaedic Surgery, Carolinas Medical Center, Charlotte

The Journal of Bone & Joint Surgery. 1996; 78:1702-6

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Abstract

Anteroposterior and lateral plain radiographs of 116 osteonecrotic femoral heads were reviewed to assess the interobserver reliability and intraobserver reproducibility of the modified Ficat classification system. The radiographs were reviewed initially and then again six months later by three adult reconstructive surgeons, two general orthopaedic surgeons, two orthopaedic residents, and one musculoskeletal radiologist.All eight observers agreed on the classification of twenty hips (17 per cent) at both the first and the second review of the radiographs. Paired comparisons revealed a mean interobserver kappa reliability coefficient of 0.46 (range, 0.30 to 0.67) for the first review and 0.45 (range, 0.30 to 0.66) for the second. For all observers, the mean rate of perfect agreement between the first and the second review was 68 per cent (range, 56 to 80 per cent). The mean kappa value for intraobserver reproducibility was 0.59 (range, 0.44 [one of the residents] to 0.73 [one of the general orthopaedic surgeons]). No observer or pair of observers had excellent reproducibility or reliability (? > 0.75).The poor interobserver reliability and fair intraobserver reproducibility diminishes any meaningful comparison of studies in which the modified Ficat classification system has been used and illuminates the need for a more reliable and reproducible classification system.

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Introduction

Introduction | Materials and Methods | Results | Discussion | References

Osteonecrosis of the femoral head has been most commonly classified according to the system of Ficat^4,7,10,11,26 and, more recently, the modified system of Ficat^15,23,33,34 (Table I). Many authors have recommended treatment on the basis of the symptoms and the Ficat classification as determined with the use of plain radiographs^{1,19,23,26,33}. Treatment with pulsed electromagnetic fields or core decompression, or both; bone-grafting and decompression; and rotational transtrochanteric osteotomy have been suggested for Ficat stage-I lesions^{1,3,15,23,25,28,29,32,33}. These procedures as well as vascularized fibular grafting, rotational transtrochanteric osteotomy, and intertrochanteric osteotomy have been recommended for stages IIA and IIB^{1,3,12,18,25,26,28,29,32-34}. All of these procedures as well as use of surface replacement and total hip replacement have been recommended to treat stage-III lesions^{1,3,6,12,16,18,19,25,26,29,34}. Pulsed electromagnetic fields, surface replacement, and total hip replacement have been recommended for the treatment of stage-IV lesions^3,6,13,16.

The choice of treatment and the judgment of its efficacy often are based directly on the Ficat stage. Determination of the Ficat stage, therefore, has important consequences, as it has a direct effect on the patient's clinical course.

A classification system is a means of description that should be biologically meaningful and be reproducible from one observer to the next as well as by one observer on separate occasions. The absence of reproducibility clouds the comprehension and comparison of studies and treatment recommendations that are based on such a classification system. The purpose of the present study was to assess the degree of interobserver reliability and intraobserver reproducibility of the modified Ficat classification system for osteonecrosis of the femoral head.

*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.

†Peachtree Orthopaedic Clinic, 2001 Peachtree Road, N. E., Suite 705, Atlanta, Georgia 30309.

‡Department of Orthopaedic Surgery, Carolinas Medical Center, 1000 Blythe Boulevard, Charlotte, North Carolina 28232.

§Miller Orthopaedic Clinic, 1001 Blythe Boulevard, Charlotte, North Carolina 28232.

¶Tennessee Orthopaedic Associates, 301 21st Avenue North, Nashville, Tennessee 37203.

*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.

†Peachtree Orthopaedic Clinic, 2001 Peachtree Road, N. E., Suite 705, Atlanta, Georgia 30309.

‡Department of Orthopaedic Surgery, Carolinas Medical Center, 1000 Blythe Boulevard, Charlotte, North Carolina 28232.

§Miller Orthopaedic Clinic, 1001 Blythe Boulevard, Charlotte, North Carolina 28232.

¶Tennessee Orthopaedic Associates, 301 21st Avenue North, Nashville, Tennessee 37203.

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TABLE I CLASSIFICATION OF OSTEONECROSIS OF THE FEMORAL HEAD

Ficat Stage⁷	Modified Ficat Stage	Findings on Plain Radiographs
I	I	Normal or, at most, minor changes (subtle loss of clarity, blurring of trabecular pattern, slight patchy osteoporosis)
II	IIA	Diffuse or localized osteoporosis, sclerosis, or cysts of femoral head
Transition	IIB	Crescentic subchondral line, segmental flattening of femoral head (out-of-round appearance)
III	III	Sequestrum, break in articular cartilage from one end of affected area to other, normal or increased joint space
IV	IV	Decreased joint space, collapse of femoral head, acetabular osteoarthrotic changes

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TABLE I CLASSIFICATION OF OSTEONECROSIS OF THE FEMORAL HEAD

Ficat Stage⁷	Modified Ficat Stage	Findings on Plain Radiographs
I	I	Normal or, at most, minor changes (subtle loss of clarity, blurring of trabecular pattern, slight patchy osteoporosis)
II	IIA	Diffuse or localized osteoporosis, sclerosis, or cysts of femoral head
Transition	IIB	Crescentic subchondral line, segmental flattening of femoral head (out-of-round appearance)
III	III	Sequestrum, break in articular cartilage from one end of affected area to other, normal or increased joint space
IV	IV	Decreased joint space, collapse of femoral head, acetabular osteoarthrotic changes

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TABLE II INTRAOBSERVER REPRODUCIBILITY FOR CLASSIFICATION OF THE ONE HUNDRED AND SIXTEEN HIPS

			Intraobserver Reproducibility
Reviewer	Position	Years of Experience	Kappa Value	Per Cent Perfect Agreement
1	General orthopaedic surgeon	20	0.73	80
2	Adult reconstructive surgeon	10	0.66	74
3	Musculoskeletal radiologist	9	0.62	70
4	Adult reconstructive surgeon	8	0.58	68
5	Adult reconstructive surgeon	5	0.56	65
6	General orthopaedic surgeon	15	0.55	65
7	Fifth-year orthopaedic resident	0	0.54	66
8	Fifth-year orthopaedic resident	0	0.44	56

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TABLE II INTRAOBSERVER REPRODUCIBILITY FOR CLASSIFICATION OF THE ONE HUNDRED AND SIXTEEN HIPS

			Intraobserver Reproducibility
Reviewer	Position	Years of Experience	Kappa Value	Per Cent Perfect Agreement
1	General orthopaedic surgeon	20	0.73	80
2	Adult reconstructive surgeon	10	0.66	74
3	Musculoskeletal radiologist	9	0.62	70
4	Adult reconstructive surgeon	8	0.58	68
5	Adult reconstructive surgeon	5	0.56	65
6	General orthopaedic surgeon	15	0.55	65
7	Fifth-year orthopaedic resident	0	0.54	66
8	Fifth-year orthopaedic resident	0	0.44	56

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TABLE III INTEROBSERVER RELIABILITY AND INTRAOBSERVER REPRODUCIBILITY FOR ORTHOPAEDIC CLASSIFICATION SYSTEMS REPORTED IN THE LITERATURE

Study	Year	Classification System Used	Interobserver Reliability	Intraobserver Reproducibility
Siebenrock and Gerber²²	1993	Neer (proximal humeral fracture)	? = 0.40	? = 0.60
		AO/ASIF	? = 0.53	? = 0.58
Sidor et al.²¹	1993	Neer (proximal humeral fracture)	? = 0.50	? = 0.66
Thomsen et al.³¹	1991	Lauge-Hansen	? = 0.55	? = 0.65
		Weber	? = 0.57	? = 0.69
Andersen et al.²	1990	Evans (intertrochanteric femoral fracture)	? = 0.51	? = 0.62
Nielsen et al.¹⁷	1990	Lauge-Hansen	43% agreement	73% agreement
Frandsen et al.⁹	1988	Garden	22% agreement	—
Kay et al.¹⁴	1994	Ficat	? = 0.56	? = 0.82

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TABLE III INTEROBSERVER RELIABILITY AND INTRAOBSERVER REPRODUCIBILITY FOR ORTHOPAEDIC CLASSIFICATION SYSTEMS REPORTED IN THE LITERATURE

Study	Year	Classification System Used	Interobserver Reliability	Intraobserver Reproducibility
Siebenrock and Gerber²²	1993	Neer (proximal humeral fracture)	? = 0.40	? = 0.60
		AO/ASIF	? = 0.53	? = 0.58
Sidor et al.²¹	1993	Neer (proximal humeral fracture)	? = 0.50	? = 0.66
Thomsen et al.³¹	1991	Lauge-Hansen	? = 0.55	? = 0.65
		Weber	? = 0.57	? = 0.69
Andersen et al.²	1990	Evans (intertrochanteric femoral fracture)	? = 0.51	? = 0.62
Nielsen et al.¹⁷	1990	Lauge-Hansen	43% agreement	73% agreement
Frandsen et al.⁹	1988	Garden	22% agreement	—
Kay et al.¹⁴	1994	Ficat	? = 0.56	? = 0.82

Materials and Methods

Introduction | Materials and Methods | Results | Discussion | References

One hundred and twenty-one symptomatic, untreated, osteonecrotic femoral heads were assessed consecutively with standard anteroposterior and lateral plain radiographs at our clinics between 1988 and 1993. Hips that did not have any radiographic changes had changes evident on magnetic resonance imaging that were consistent with osteonecrosis²⁰. The acceptability of each radiograph was determined by an orthopaedic surgeon who was not an observer in this study. The radiographs of five hips were determined to be unacceptable; therefore, 116 hips were included in the study. All identifying data on the radiographs were obscured, and the radiographs were numbered randomly.

Each radiograph was reviewed and classified by eight observers: three adult orthopaedic reconstructive surgeons, two general orthopaedic surgeons, two fifth-year orthopaedic residents, and one musculoskeletal radiologist. All of the observers were familiar with the Ficat classification system⁷ and had used it in clinical situations previously.

One week before the radiographic review, each observer was provided with and asked to review a copy of Ficat's description of his classification system⁷ and each was given information regarding the modified Ficat system. The observers were also provided with a copy of the classification system during testing and were allowed to refer to this as often as necessary. No questions or discussion were allowed during or after testing, and the observers were given as much time as they needed to review each radiograph. After a decision had been made, the radiographs of the next hip were presented until all 116 hips had been classified.

The radiographs were classified by each observer on two separate occasions, six months apart. In the interim, the radiographs were not available to any of the observers and no feedback was provided. The second review was performed in a similar manner, except that the order of the radiographs was reversed.

Statistical Analysis

Computer-assisted statistical analysis (BMDP Statistical Software, PC Version; University of California, Berkeley, California) was used to determine interobserver and intraobserver variability. Kappa values were generated by setting the observed proportion of agreement in relation to the proportion of agreement expected by chance. The kappa coefficients ranged from +1.0 (complete agreement) to 0.0 (chance agreement) to less than 0.0 (less agreement than expected by chance)⁸.

The guidelines of Svanholm et al. were used for interpretation of the kappa values³⁰. Values of less than 0.50 indicated poor agreement and those of more than 0.75 indicated excellent agreement.

Accuracy, or how close an experimental observation lies to a true value, was impossible to measure because the correct classification for each osteonecrotic hip was not known. We therefore assessed the level of agreement between paired observers (interobserver reliability) and between the reviews of the same observer (intraobserver reproducibility) over time.

Results

Introduction | Materials and Methods | Results | Discussion | References

Interobserver Reliability

During the first and second reviews of the radiographs, all eight observers agreed on the classification of only twenty hips (17 per cent): eleven were stage IV, one was stage III, two were stage IIA, and six were stage I. Seven of the eight observers agreed on thirty-nine hips (34 per cent) during the first review and on thirty-five hips (30 per cent) during the second. When the level of agreement was lowered to a majority (five of eight observers) level, the observers agreed on eighty-five hips (73 per cent) and eighty-four hips (72 per cent) during the first and second reviews, respectively.

Paired comparisons among the classifications of the eight observers for each radiograph produced twenty-eight paired analyses for each of the two reviews of the radiographs. The mean interobserver reliability coefficient was 0.46 (range, 0.30 to 0.67) for the first review and 0.45 (range, 0.30 to 0.66) for the second. The mean reliability coefficient with respect to the level of expertise was 0.41 for the orthopaedic residents, 0.51 for the adult reconstructive surgeons (who had a mean of 7.7 years of experience), and 0.60 for the general orthopaedic surgeons (who had twenty and fifteen years of experience).

Intraobserver Reproducibility

Assessment of the data for all eight observers revealed an average of thirty-seven instances (32 per cent) in which the classification of a hip at the first review differed from that at the second. Changes were more common when the hip had initially been assigned a middle stage: 31 per cent (nine) of the twenty-nine hips that had been classified initially as stage IIA, eight of the seventeen hips that had been classified as stage IIB (transition), and 39 per cent (nine) of the twenty-three hips that had been classified as stage III were classified differently at the second review. In comparison, two of the eleven hips that had been classified as stage I and 19 per cent (seven) of the thirty-six hips that had been classified as stage IV were classified differently at the second review.

The mean kappa intraobserver reproducibility coefficient was 0.59 (range, 0.44 to 0.73) among the eight observers (Table II). The mean reproducibility was 0.60 (0.66, 0.58, and 0.56) for the adult reconstructive surgeons, 0.49 (0.54 and 0.44) for the orthopaedic residents, and 0.62 (0.73 and 0.55) for the general orthopaedic surgeons. The mean perfect agreement between the first and the second review was 68 per cent (range, 56 to 80 per cent).

Paired comparison of the two observers with the highest reproducibility revealed kappa reliability coefficients of 0.49 and 0.55 during the first and second reviews, respectively.

Discussion

Introduction | Materials and Methods | Results | Discussion | References

Orthopaedic classification systems provide subdivisions in the spectrum of presentation of certain disease processes. These subdivisions, in turn, may be studied individually with respect to diagnosis, treatment, prognosis, and outcome. For such a classification system to be useful, it must be reproducible among different observers as well as by the same observer on separate occasions. Without these qualities, a precise language on which scientific study and comparison can be based is impossible.

Reported evaluations of orthopaedic classification systems^{2,5,9,17,21,22,31} have yielded disappointing results, with kappa values ranging from 0.40 to 0.57 for interobserver reliability and from 0.58 to 0.69 for intraobserver reproducibility. Recently, Kay et al. reported a kappa statistic of 0.82 for intraobserver variability and 0.56 for interobserver variability for twenty-five hips that were assessed with use of the Ficat classification system on three occasions by six observers¹⁴ (Table III).

Svanholm et al. stated that "since we are dealing with the minimal requirement that the criteria under study are reproducible, and since the lower limit of the reproducibility defines the upper limit of the significance of the parameter in biological terms, we advocate that ? = 0.50 should be taken as poor, and ? = 0.75 as excellent reproducibility."³⁰ We modified this scheme so that kappa values that were between 0.50 and 0.75 were interpreted as fair. According to these modified guidelines, the present study demonstrated poor interobserver reliability and fair intraobserver reproducibility, with no instances of excellent intraobserver reproducibility or interobserver reliability. In simpler terms, during approximately one of every three reviews, an educated observer classified an osteonecrotic hip differently than a colleague did and, in fact, differently than he himself had classified the hip six months previously.

The observers were least likely to change their classification of hips that they had initially classified as stage I or IV, presumably because these stages represent clear visual images of either a normal hip without changes or a severely osteonecrotic hip with dramatic changes. Hips that were classified initially as stage IIA, stage IIB (transition), or stage III were twice as likely to be classified differently by the same observer than those classified as stage I or IV. While we did not address the reasons for this, the discrepancy may result from various interpretations of the phrases used in Ficat's original description of the middle stages⁷, such as diffuse sclerosis in the description of stage II; crescentic line, segmental flattening (or out-of-round appearance) in the description of transition; and sequestrum and collapse in the description of stage III.

The spectrum of the osteonecrotic disease process, stratified into rigid classifications, creates inevitable gray areas at the boundaries of each grade. The use of language to describe a radiograph is fraught with imprecision and is subject to the observer's interpretation of both the language and the radiograph. An out-of-round appearance to one observer may be collapse to another. These gray areas and the various interpretations of Ficat's language cause variability in the application of this classification system.

These results, especially with regard to the middle stages of classification, are important and disturbing for several reasons. In the absence of excellent interobserver reliability, it is not sound to compare studies of similarly classified hips from different centers³⁰. Also, in the absence of excellent intraobserver reproducibility, it is not sound to rely on outcome studies that are based on plain radiographs that were assessed over a period of time, before and after treatment, within the same center, or by the same observer or group of observers.

Many methods of treatment for the various stages of osteonecrosis of the femoral head have been described, with variable results^{1,3,15,16,18,19,23-29,32-34}. Widely divergent recommendations for treatment as well as greatly differing prognoses often are based on use of the Ficat classification as it reflects the presence or absence of subchondral, segmental, or advanced collapse of the femoral head. It is reasonable to assume that one cause of the present conflict in treatment recommendations is the different interpretation and use of the Ficat classification by different investigators.

The modified Ficat classification for osteonecrosis of the femoral head does not have acceptable interobserver reliability and intraobserver reproducibility on which to base treatment protocols and determinations of outcome. Magnetic resonance imaging and computed tomography offer a more detailed view of the involvement of the femoral head, subchondral collapse, narrowing of the joint space, and acetabular changes found with the progression of this disease. Future treatment recommendations and outcome analysis may be more reliably and reproducibly based on these imaging techniques.

NOTE: The authors give special thanks to Walter B. Beaver, M.D.; James Coumas, M.D.; Thomas K. Fehring, M.D.; Forney Hutchinson, III, M.D.; and Jeffrey G. Mokris, M.D., for participating in the study. The authors also thank Kim Gravitte for her technical assistance in the statistical analysis of the data.

References

Introduction | Materials and Methods | Results | Discussion | References

Aaron, R. K.; Lennox, D.; Bunce, G. E.; and |and |Ebert, T.: The conservative treatment of osteonecrosis of the femoral head. A comparison of core decompression and pulsing electromagnetic fields. Clin. Orthop.,249: 209-218, 1989.249209 1989 [PubMed]

Andersen, E.; Jorgensen, L. G.; and |and |Hededam, L. T.: Evans' classification of trochanteric fractures: an assessment of the interobserver and intraobserver reliability. Injury,21: 377-378, 1990.21377 1990 [PubMed][CrossRef]

Bassett, C. A. L.; Schink-Ascani, M.; and |and |Lewis, S. M.: Effects of pulsed electromagnetic fields on Steinberg ratings of femoral head osteonecrosis. Clin. Orthop.,246: 172-185, 1989.246172 1989 [PubMed]

Camp, J. F., and |and |Colwell, C. W., Jr.: Core decompression of the femoral head for osteonecrosis. J. Bone and Joint Surg.,68-A: 1313-1319, Dec. 1986.68-A1313 1986

Dias, J. J.; Taylor, M.; Thompson, J.; Brenkel, I. J.; and |and |Gregg, P. J.: Radiographic signs of union of scaphoid fractures. An analysis of inter-observer agreement and reproducibility. J. Bone and Joint Surg.,70-B(2): 299-301, 1988.70-B(2)299 1988

Dutton, R. O.; Amstutz, H. C.; Thomas, B. J.; and |and |Hedley, A. K.: Tharies surface replacement for osteonecrosis of the femoral head. J. Bone and Joint Surg.,64-A: 1225-1237, Oct. 1982.64-A1225 1982

Ficat, R. P.: Idiopathic bone necrosis of the femoral head. Early diagnosis and treatment. J. Bone and Joint Surg.,67-B(1): 3-9, 1985.67-B(1)3 1985

Fleiss, J. L.: Statistical Methods for Rates and Proportions. Ed. 2, p. 217. New York, John Wiley and Sons, 1981.

Frandsen, P. A.; Andersen, E.; Madsen, F.; and |and |Skjodt, T.: Garden's classification of femoral neck fractures. An assessment of inter-observer variation. J. Bone and Joint Surg.,70-B(4): 588-590, 1988.70-B(4)588 1988

Hopson, C. N., and |and |Siverhus, S. W.: Ischemic necrosis of the femoral head. Treatment by core decompression. J. Bone and Joint Surg.,70-A: 1048-1051, Aug. 1988.70-A1048 1988

Hungerford, D. S., and Lennox, D. W.: Diagnosis and treatment of ischemic necrosis of the femoral head. In Surgery of the Musculoskeletal System, edited by C. McC. Evarts. Ed. 2, vol. 3, pp. 2757-2794. New York, Churchill Livingstone, 1990.

Jacobs, M. A.; Hungerford, D. S.; and |and |Krackow, K. A.: Intertrochanteric osteotomy for avascular necrosis of the femoral head. J. Bone and Joint Surg.,71-B(2): 200-204, 1989.71-B(2)200 1989

Katz, R. L.; Bourne, R. B.; Rorabeck, C. H.; and |and |McGee, H.: Total hip arthroplasty in patients with avascular necrosis of the hip. Follow-up observations on cementless and cemented operations. Clin. Orthop.,281: 145-151, 1992.281145 1992 [PubMed]

Kay, R. M.; Lieberman, J. R.; Dorey, F. J.; and |and |Seeger, L. L.: Inter- and intraobserver variation in staging patients with proven avascular necrosis of the hip. Clin. Orthop.,307: 124-129, 1994.307124 1994 [PubMed]

Lennox, D. W.; Murrah, R. L.; Ebert, T.; and |and |Carbone, J.: The efficacy and safety of core decompression of the hip as a treatment for osteonecrosis. Complicat. Orthop.,47: 39-42, 47, 1993.4739 1993

Meyers, M. H.: Osteonecrosis of the femoral head. Pathogenesis and long-term results of treatment. Clin. Orthop.,231: 51-61, 1988.23151 1988 [PubMed]

Nielsen, J. O.; Dons-Jensen, H.; and |and |Sorensen, H. T.: Lauge-Hansen classification of malleolar fractures. An assessment of the reproducibility in 118 cases. Acta Orthop. Scandinavica,61: 385-387, 1990.61385 1990 [CrossRef]

Saito, S.; Ohzono, K.; and |and |Ono, K.: Joint-preserving operations for idiopathic avascular necrosis of the femoral head. J. Bone and Joint Surg.,70-B(1): 78-84, 1988.70-B(1)78 1988

Scher, M. A., and |and |Jakim, I.: Intertrochanteric osteotomy and autogenous bone-grafting for avascular necrosis of the femoral head. J. Bone and Joint Surg.,75-A: 1119-1133, Aug. 1993.75-A1119 1993

Seiler, J. G., III; Christie, M. J.; and |and |Homra, L.: Correlation of the findings of magnetic resonance imaging with those of bone biopsy in patients who have stage-I or II ischemic necrosis of the femoral head. J. Bone and Joint Surg.,71-A: 28-32, Jan. 1989.71-A28 1989

Sidor, M. L.; Zuckerman, J. D.; Lyon, T.; Koval, K.; Cuomo, F.; and |and |Schoenberg, N.: The Neer classification system for proximal humeral fractures. An assessment of interobserver reliability and intraobserver reproducibility. J. Bone and Joint Surg.,75-A: 1745-1750, Dec. 1993.75-A1745 1993

Siebenrock, K. A., and |and |Gerber, C.: The reproducibility of classification of fractures of the proximal end of the humerus. J. Bone and Joint Surg.,75-A: 1751-1755, Dec. 1993.75-A1751 1993

Smith, S. W.; Fehring, T. K.; Griffin, W. L.; and |and |Beaver, W. B.: Core decompression of the osteonecrotic femoral head. J. Bone and Joint Surg.,77-A: 674-680, May 1995.77-A674 1995

Steinberg, M. E.: Management of avascular necrosis of the femoral head—an overview. In Instructional Course Lectures, The American Academy of Orthopaedic Surgeons. Vol. 37, pp. 41-50. St. Louis, C. V. Mosby, 1988.

Steinberg, M. E.; Brighton, C. T.; Corces, A.; Hayken, G. D.; Steinberg, D. R.; Strafford, B.; Tooze, S. E.; and |and |Fallon, M.: Osteonecrosis of the femoral head. Results of core decompression and grafting with and without electrical stimulation. Clin. Orthop.,249: 199-208, 1989.249199 1989 [PubMed]

Stulberg, B. N.; Davis, A. W.; Bauer, T. W.; Levine, M.; and |and |Easley, K.: Osteonecrosis of the femoral head. A prospective randomized treatment protocol. Clin. Orthop.,268: 140-151, 1991.268140 1991 [PubMed]

Stulberg, B. N.; Levine, M.; Bauer, T. W.; Belhobek, G. H.; Pflanze, W.; Feiglin, D. H. I.; and |and |Roth, A. I.: Multimodality approach to osteonecrosis of the femoral head. Clin. Orthop.,240: 181-193, 1989.240181 1989 [PubMed]

Sugano, N.; Takaoka, K.; Ohzono, K.; Matsui, M.; Saito, M.; and |and |Saito, S.: Rotational osteotomy for non-traumatic avascular necrosis of the femoral head. J. Bone and Joint Surg.,74-B(5): 734-739, Sept. 1992.74-B(5)734 1992

Sugioka, Y.; Hotokebuchi, T.; and |and |Tsutsui, H.: Transtrochanteric anterior rotational osteotomy for idiopathic and steroid-induced necrosis of the femoral head. Indications and long-term results. Clin. Orthop.,277: 111-120, 1992.277111 1992 [PubMed]

Svanholm, H.; Starklint, H.; Gundersen, H. J. G.; Fabricius, J.; Barlebo, H.; and |and |Olsen, S.: Reproducibility of histomorphologic diagnoses with special reference to the kappa statistic. APMIS,97: 689-698, 1989.97689 1989 [PubMed][CrossRef]

Thomsen, N. O. B.; Overgaard, S.; Olsen, L. H.; Hansen, H.; and |and |Nielsen, S. T.: Observer variation in the radiographic classification of ankle fractures. J. Bone and Joint Surg.,73-B(4): 676-678, 1991.73-B(4)676 1991

Tooke, S. M. T.; Nugent, P. J.; Bassett, L. W.; Nottingham, P.; Mirra, J.; and |and |Jinnah, R.: Results of core decompression for femoral head osteonecrosis. Clin. Orthop.,228: 99-104, 1988.22899 1988 [PubMed]

Warner, J. J. P.; Philip, J. H.; Brodsky, G. L.; and |and |Thornhill, T. S.: Studies of nontraumatic osteonecrosis. The role of core decompression in the treatment of nontraumatic osteonecrosis of the femoral head. Clin. Orthop.,225: 104-127, 1987.225104 1987 [PubMed]

Yoo, M. C.; Chung, D. W.; and |and |Hahn, C. S.: Free vascularized fibula grafting for the treatment of osteonecrosis of the femoral head. Clin. Orthop.,277: 128-138, 1992.277128 1992 [PubMed]

Topics

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TABLE I CLASSIFICATION OF OSTEONECROSIS OF THE FEMORAL HEAD

Ficat Stage⁷	Modified Ficat Stage	Findings on Plain Radiographs
I	I	Normal or, at most, minor changes (subtle loss of clarity, blurring of trabecular pattern, slight patchy osteoporosis)
II	IIA	Diffuse or localized osteoporosis, sclerosis, or cysts of femoral head
Transition	IIB	Crescentic subchondral line, segmental flattening of femoral head (out-of-round appearance)
III	III	Sequestrum, break in articular cartilage from one end of affected area to other, normal or increased joint space
IV	IV	Decreased joint space, collapse of femoral head, acetabular osteoarthrotic changes

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TABLE I CLASSIFICATION OF OSTEONECROSIS OF THE FEMORAL HEAD

Ficat Stage⁷	Modified Ficat Stage	Findings on Plain Radiographs
I	I	Normal or, at most, minor changes (subtle loss of clarity, blurring of trabecular pattern, slight patchy osteoporosis)
II	IIA	Diffuse or localized osteoporosis, sclerosis, or cysts of femoral head
Transition	IIB	Crescentic subchondral line, segmental flattening of femoral head (out-of-round appearance)
III	III	Sequestrum, break in articular cartilage from one end of affected area to other, normal or increased joint space
IV	IV	Decreased joint space, collapse of femoral head, acetabular osteoarthrotic changes

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TABLE II INTRAOBSERVER REPRODUCIBILITY FOR CLASSIFICATION OF THE ONE HUNDRED AND SIXTEEN HIPS

			Intraobserver Reproducibility
Reviewer	Position	Years of Experience	Kappa Value	Per Cent Perfect Agreement
1	General orthopaedic surgeon	20	0.73	80
2	Adult reconstructive surgeon	10	0.66	74
3	Musculoskeletal radiologist	9	0.62	70
4	Adult reconstructive surgeon	8	0.58	68
5	Adult reconstructive surgeon	5	0.56	65
6	General orthopaedic surgeon	15	0.55	65
7	Fifth-year orthopaedic resident	0	0.54	66
8	Fifth-year orthopaedic resident	0	0.44	56

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TABLE II INTRAOBSERVER REPRODUCIBILITY FOR CLASSIFICATION OF THE ONE HUNDRED AND SIXTEEN HIPS

			Intraobserver Reproducibility
Reviewer	Position	Years of Experience	Kappa Value	Per Cent Perfect Agreement
1	General orthopaedic surgeon	20	0.73	80
2	Adult reconstructive surgeon	10	0.66	74
3	Musculoskeletal radiologist	9	0.62	70
4	Adult reconstructive surgeon	8	0.58	68
5	Adult reconstructive surgeon	5	0.56	65
6	General orthopaedic surgeon	15	0.55	65
7	Fifth-year orthopaedic resident	0	0.54	66
8	Fifth-year orthopaedic resident	0	0.44	56

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TABLE III INTEROBSERVER RELIABILITY AND INTRAOBSERVER REPRODUCIBILITY FOR ORTHOPAEDIC CLASSIFICATION SYSTEMS REPORTED IN THE LITERATURE

Study	Year	Classification System Used	Interobserver Reliability	Intraobserver Reproducibility
Siebenrock and Gerber²²	1993	Neer (proximal humeral fracture)	? = 0.40	? = 0.60
		AO/ASIF	? = 0.53	? = 0.58
Sidor et al.²¹	1993	Neer (proximal humeral fracture)	? = 0.50	? = 0.66
Thomsen et al.³¹	1991	Lauge-Hansen	? = 0.55	? = 0.65
		Weber	? = 0.57	? = 0.69
Andersen et al.²	1990	Evans (intertrochanteric femoral fracture)	? = 0.51	? = 0.62
Nielsen et al.¹⁷	1990	Lauge-Hansen	43% agreement	73% agreement
Frandsen et al.⁹	1988	Garden	22% agreement	—
Kay et al.¹⁴	1994	Ficat	? = 0.56	? = 0.82

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TABLE III INTEROBSERVER RELIABILITY AND INTRAOBSERVER REPRODUCIBILITY FOR ORTHOPAEDIC CLASSIFICATION SYSTEMS REPORTED IN THE LITERATURE

Study	Year	Classification System Used	Interobserver Reliability	Intraobserver Reproducibility
Siebenrock and Gerber²²	1993	Neer (proximal humeral fracture)	? = 0.40	? = 0.60
		AO/ASIF	? = 0.53	? = 0.58
Sidor et al.²¹	1993	Neer (proximal humeral fracture)	? = 0.50	? = 0.66
Thomsen et al.³¹	1991	Lauge-Hansen	? = 0.55	? = 0.65
		Weber	? = 0.57	? = 0.69
Andersen et al.²	1990	Evans (intertrochanteric femoral fracture)	? = 0.51	? = 0.62
Nielsen et al.¹⁷	1990	Lauge-Hansen	43% agreement	73% agreement
Frandsen et al.⁹	1988	Garden	22% agreement	—
Kay et al.¹⁴	1994	Ficat	? = 0.56	? = 0.82