- Email: [email protected]
Assessment of articular cartilage of the lateral tibial plateau in varus osteoarthritis of the knee
The Knee 7 Ž2000. 217᎐220
Original article
Assessment of articular cartilage of the lateral tibial plateau in varus osteoarthritis of the knee Takehiko SugitaU , Takeshi Chiba, Tomomaro Kawamata, Masahiro Ohnuma, Yusuke Yoshizumi Department of Orthopaedic Surgery, Tohoku Uni¨ ersity Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan Received 19 April 2000; received in revised form 6 September 2000; accepted 11 September 2000
Abstract This study describes the soft X-ray examinations of 24 lateral tibial plateaus obtained during total knee arthroplasty for varus osteoarthritis. The average thickness of the articular cartilage was 3.5 min and ranged from 2.1 to 5.0. We considered that 21 out of the 24 lateral tibial plateaus had well preserved articular cartilage. Within the well preserved articular cartilage, bony protuberances of various sizes were found in five cases. All lateral tibial plateaus except one showed osteophyte formation. We considered that 12 of the 24 lateral tibial plateaus had large osteophytes. Ten of these 12 lateral tibial plateaus had well preserved articular cartilage. Large osteophyte formation may not necessarily be a contra-indication of high tibial osteotomy ŽHTO. or unicompartmental knee arthroplasty ŽUKA.. Cases with a bony protuberance may not be suitable for HTO or UKA, because the overlying articular cartilage is thin and inadequate for supporting load. 䊚 2000 Elsevier Science B.V. All rights reserved. Keywords: Articular cartilage; Bony protuberance; Lateral tibial plateau; Osteoarthritis; Varus; Knee
1. Introduction The available operative procedures for osteoarthritis of the knee include high tibial osteotomy ŽHTO., unicompartmental knee arthroplasty ŽUKA. and total knee arthroplasty. In choosing HTO or UKA for osteoarthritis, it is first necessary to confirm that the uninvolved compartment has few degenerative changes w1᎐4x. To clinically assess the status of the articular cartilage in the uninvolved compartment, Laskin w1x used the preoperative radiographic criteria described by Coventry. Gibson et al. w2x recommended stress radio-
graphy and Kozinn w3x relied on the intraoperative findings. However, it is difficult to assess the thickness of the articular cartilage or the degenerative changes inside it directly by their methods. Brocklehurst et al. w4x biochemically analyzed the articular cartilage from osteoarthritic and normal control adult human knee joints. Obeid et al. w5x studied the mechanical properties of cartilage from the apparently unaffected compartments of knees with unicompartmental osteoarthritis. In this study, we investigated the articular cartilage of the lateral tibial plateaus of varus osteoarthritis by soft X-ray. 2. Materials and methods
U
Corresponding author. Tel.: q81-22-717-7245; fax: q81-22717-7248. E-mail address: [email protected] ŽT. Sugita..
Twenty-four lateral tibial plateaus were obtained during total knee arthroplasty for patients of varus
0968-0160r00r$ - see front matter 䊚 2000 Elsevier Science B.V. All rights reserved. PII: S 0 9 6 8 - 0 1 6 0 Ž 0 0 . 0 0 0 6 5 - X
218
T. Sugita et al. r The Knee 7 (2000) 217᎐220
Fig. 2. The thickness of the articular cartilage was well preserved on soft X-ray. It was measured at the thickest portion Žarrow..
Fig. 1. An approximately 5-mm thick sagittal slice at the center of the lateral tibial plateau Žasterisk. was obtained. Osteophytes were found at the junction of the anterior and middle part of the lateral tibial plateau Žarrow..
osteoarthritis. There were five males and 19 females. The average age at the time of operation was 68 years and ranged from 58 to 76 years. In none of the 24 knees was the medial joint space visible on the posteroanterior weight-bearing radiographs performed according to Rosenberg et al. w6x. Approximately 5-mm thick sagittal slices at the center of the lateral tibial plateaus were sectioned ŽFig. 1. and soft X-rays were taken of them. In almost all slices, the articular cartilage was well preserved. The thickness of the cartilage was measured. As the thickness differed from place to place, the thickest portion was adopted as the thickness ŽFig. 2.. Because there were no normal control subjects, the thicknesses of our cases were compared with that reported by Obeid et al. w5x. 3. Results Subchondral bone was not exposed in any of the
lateral tibial plateaus. The average thickness of the articular cartilage was 3.5 mm and ranged from 2.1 to 5.0 mm. Obeid et al. w5x reported that the mean thickness of the articular cartilage from the weightbearing area at the center of the lateral tibial plateau in normal knees was 3.29" 0.78 mm Žmean " 1 S.D... The thickness of the articular cartilage of 21 out of 24 lateral tibial plateaus was greater than 2.51 mm Žmean y 1 S.D... We considered that these 21 lateral tibial plateaus had well preserved articular cartilage, although surfaces of the articular cartilage in five of these 21 cases were not smooth. The articular cartilage in the remaining three showed severe degeneration or attrition ŽFig. 3.. Within the well preserved articular cartilage of these 21 lateral tibial plateaus, bony protuberances of various sizes were found in five cases ŽFig. 4.. The subchondral plate was left intact between the bony protuberance and subchondral bone. The surface of the articular cartilage overlying the bony protuberance was irregular in four of these five cases. All lateral tibial plateaus except one showed osteophyte formation. In 21 cases, osteophytes were found at the junction of the anterior and middle part of the lateral tibial plateaus ŽFig. 1., and in two cases, osteophytes were also found at the posterior margin of the
Fig. 3. Articular cartilage showing severe degeneration or attrition on soft X-ray.
T. Sugita et al. r The Knee 7 (2000) 217᎐220
Fig. 4. Various sizes of bony protuberances were found within the well preserved articular cartilage on soft X-ray.
plateau as well. The heights of the osteophytes averaged 4.2 mm and ranged from 1.8 to 7.8 mm ŽFig. 5.. We considered that 12 of the 24 lateral tibial plateaus had large osteophytes, which were higher than 4.2 mm. Even if the lateral tibial plateaus had large osteophytes, they had well preserved articular cartilage in 10 of 12 cases.
4. Discussion Although HTO and UKA are useful operative procedures for osteoarthritis of the knee, a major problem is the assessment of the status of the articu-
219
lar cartilage in the uninvolved compartment, as Laskin w1x already pointed out in 1978. Laskin w1x used the preoperative radiographic criteria described by Coventry: namely, no sclerosis, cystic changes, or large spurs on the uninvolved side. Gibson et al. w2x suggested the importance of stress radiography for the accurate assessment of the uninvolved compartment in degenerative arthritis of the knee when planning operative treatment. They stated that if the joint space of the uninvolved compartment on stress radiographs was 5 mm or more, the articular cartilage in that compartment should be considered normal. Kozinn et al. w3x recommended that the final decision to perform UKA had to be made after an arthrotomy had been done and the articular surfaces had been examined. In this study, we investigated the sagittal slices at the center of the lateral tibial plateaus in varus osteoarthritis by soft X-ray. Laskin w1x considered large spur formation to be a factor that indicated degenerative changes of the uninvolved compartment. However, 10 of 12 lateral tibial plateaus that had large osteophytes showed well preserved articular cartilage on soft X-rays. As the center of the lateral tibial plateau is considered to become the weight-bearing area when the knee is in valgus alignment, large osteophyte formation may not necessarily be a contra-indication to HTO or UKA. Gibson et al. w2x stated that a preserved joint space on stress radiography was a factor that indicated normal articular cartilage. Their methods could only evaluate the thickness of the articular cartilage. However, we found a bony protuberance within the articular cartilage in five of 21 cases that showed well-preserved articular cartilage. The bony protuberance can be recognized neither by stress radiography as described by Gibson et al. w2x nor by the visual appearance of the articular surface as recommended by Kozinn et al. w3x because it exists within the articular cartilage.
Fig. 5. The height of an osteophyte was defined as the distance from the subchondral plate to the top of the osteophyte.
220
T. Sugita et al. r The Knee 7 (2000) 217᎐220
Brocklehurst et al. w4x biochemically analyzed the articular cartilage from osteoarthritic and normal control adult human knee joints. They suggested that HTO or UKA might be rational procedures for knees in which the cartilage in all of one component was visually intact. Obeid et al. w5x studied the mechanical properties of cartilage from the apparently unaffected compartment of knees with unicompartmental osteoarthritis. They concluded that the apparently unaffected cartilage in knees with unicompartmental osteoarthritis was mechanically inferior to normal cartilage, even though clinically, radiologically, and morphologically it appeared to be sound. Although the mechanical and biochemical properties were not examined in our study, the existence of a bony protuberance must be a disadvantage for supporting load, because the thickness of the overlying articular cartilage is reduced by the bony protuberance. Accordingly, cases with a bony protuberance should not undergo HTO or UKA. How can the existence of a bony protuberance be determined clinically? To our knowledge, bony protuberances have been described only by Bergman et al. w7x as bone formation within the hyaline cartilage. However, they did not state whether these could be depicted on radiographs or MR imaging. We retrospectively examined conventional radiographs, tomograms, and MR imagings, but could not find bony protuberances on them. Mechanical or biochemical investigations on the articular cartilage with bony
protuberance are needed. Clinically, more detailed examinations may be necessary to disclose the bony protuberance preoperatively.
Acknowledgements The authors wish to thank Professor George Bentley for his kind advice. References w1 x w2x w3x w4x w5x w6x
w7x
Laskin RS. Unicompartmental tibiofemoral resurfacing arthroplasty. J Bone Joint Surg wAmx 1978;60-A:182᎐185. Gibson PH, Goodfellow JW. Stress radiography in degenerative arthritis of the knee. J Bone Joint Surg wBrx 1986;68B:608᎐609. Kozinn SC, Scott R. Unicondylar knee arthroplasty. J Bone Joint Surg wAmx 1989;71-A:145᎐150. Brocklehurst R, Bayliss MT, Maroudas A et al. The composition of normal and osteoarthritic articular cartilage from human knee joints. J Bone Joint Surg wAmx 1984;66-A:95᎐106. Obeid EMH, Adams MA, Newman JH. Mechanical properties of articular cartilage in knees with unicompartmental osteoarthritis. J Bone Joint Surg wBrx 1994;76-B:315᎐319. Rosenberg TD, Paulos LE, Parker RD, Coward DB, Scott SM. The forty-five-degree posteroanterior flexion weightbearing radiograph of the knee. J Bone Joint Surg wAmx 1988;70-A:1479᎐1483. Bergman AG, Willen HK, Lindstrand AL, Pettersson HTA. Osteoarthritis of the knee: correlation of subchondral MR signal abnormalities with histopathologic and radiographic features. Skeletal Radiol 1994;23:445᎐448.
Original article
Assessment of articular cartilage of the lateral tibial plateau in varus osteoarthritis of the knee Takehiko SugitaU , Takeshi Chiba, Tomomaro Kawamata, Masahiro Ohnuma, Yusuke Yoshizumi Department of Orthopaedic Surgery, Tohoku Uni¨ ersity Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan Received 19 April 2000; received in revised form 6 September 2000; accepted 11 September 2000
Abstract This study describes the soft X-ray examinations of 24 lateral tibial plateaus obtained during total knee arthroplasty for varus osteoarthritis. The average thickness of the articular cartilage was 3.5 min and ranged from 2.1 to 5.0. We considered that 21 out of the 24 lateral tibial plateaus had well preserved articular cartilage. Within the well preserved articular cartilage, bony protuberances of various sizes were found in five cases. All lateral tibial plateaus except one showed osteophyte formation. We considered that 12 of the 24 lateral tibial plateaus had large osteophytes. Ten of these 12 lateral tibial plateaus had well preserved articular cartilage. Large osteophyte formation may not necessarily be a contra-indication of high tibial osteotomy ŽHTO. or unicompartmental knee arthroplasty ŽUKA.. Cases with a bony protuberance may not be suitable for HTO or UKA, because the overlying articular cartilage is thin and inadequate for supporting load. 䊚 2000 Elsevier Science B.V. All rights reserved. Keywords: Articular cartilage; Bony protuberance; Lateral tibial plateau; Osteoarthritis; Varus; Knee
1. Introduction The available operative procedures for osteoarthritis of the knee include high tibial osteotomy ŽHTO., unicompartmental knee arthroplasty ŽUKA. and total knee arthroplasty. In choosing HTO or UKA for osteoarthritis, it is first necessary to confirm that the uninvolved compartment has few degenerative changes w1᎐4x. To clinically assess the status of the articular cartilage in the uninvolved compartment, Laskin w1x used the preoperative radiographic criteria described by Coventry. Gibson et al. w2x recommended stress radio-
graphy and Kozinn w3x relied on the intraoperative findings. However, it is difficult to assess the thickness of the articular cartilage or the degenerative changes inside it directly by their methods. Brocklehurst et al. w4x biochemically analyzed the articular cartilage from osteoarthritic and normal control adult human knee joints. Obeid et al. w5x studied the mechanical properties of cartilage from the apparently unaffected compartments of knees with unicompartmental osteoarthritis. In this study, we investigated the articular cartilage of the lateral tibial plateaus of varus osteoarthritis by soft X-ray. 2. Materials and methods
U
Corresponding author. Tel.: q81-22-717-7245; fax: q81-22717-7248. E-mail address: [email protected] ŽT. Sugita..
Twenty-four lateral tibial plateaus were obtained during total knee arthroplasty for patients of varus
0968-0160r00r$ - see front matter 䊚 2000 Elsevier Science B.V. All rights reserved. PII: S 0 9 6 8 - 0 1 6 0 Ž 0 0 . 0 0 0 6 5 - X
218
T. Sugita et al. r The Knee 7 (2000) 217᎐220
Fig. 2. The thickness of the articular cartilage was well preserved on soft X-ray. It was measured at the thickest portion Žarrow..
Fig. 1. An approximately 5-mm thick sagittal slice at the center of the lateral tibial plateau Žasterisk. was obtained. Osteophytes were found at the junction of the anterior and middle part of the lateral tibial plateau Žarrow..
osteoarthritis. There were five males and 19 females. The average age at the time of operation was 68 years and ranged from 58 to 76 years. In none of the 24 knees was the medial joint space visible on the posteroanterior weight-bearing radiographs performed according to Rosenberg et al. w6x. Approximately 5-mm thick sagittal slices at the center of the lateral tibial plateaus were sectioned ŽFig. 1. and soft X-rays were taken of them. In almost all slices, the articular cartilage was well preserved. The thickness of the cartilage was measured. As the thickness differed from place to place, the thickest portion was adopted as the thickness ŽFig. 2.. Because there were no normal control subjects, the thicknesses of our cases were compared with that reported by Obeid et al. w5x. 3. Results Subchondral bone was not exposed in any of the
lateral tibial plateaus. The average thickness of the articular cartilage was 3.5 mm and ranged from 2.1 to 5.0 mm. Obeid et al. w5x reported that the mean thickness of the articular cartilage from the weightbearing area at the center of the lateral tibial plateau in normal knees was 3.29" 0.78 mm Žmean " 1 S.D... The thickness of the articular cartilage of 21 out of 24 lateral tibial plateaus was greater than 2.51 mm Žmean y 1 S.D... We considered that these 21 lateral tibial plateaus had well preserved articular cartilage, although surfaces of the articular cartilage in five of these 21 cases were not smooth. The articular cartilage in the remaining three showed severe degeneration or attrition ŽFig. 3.. Within the well preserved articular cartilage of these 21 lateral tibial plateaus, bony protuberances of various sizes were found in five cases ŽFig. 4.. The subchondral plate was left intact between the bony protuberance and subchondral bone. The surface of the articular cartilage overlying the bony protuberance was irregular in four of these five cases. All lateral tibial plateaus except one showed osteophyte formation. In 21 cases, osteophytes were found at the junction of the anterior and middle part of the lateral tibial plateaus ŽFig. 1., and in two cases, osteophytes were also found at the posterior margin of the
Fig. 3. Articular cartilage showing severe degeneration or attrition on soft X-ray.
T. Sugita et al. r The Knee 7 (2000) 217᎐220
Fig. 4. Various sizes of bony protuberances were found within the well preserved articular cartilage on soft X-ray.
plateau as well. The heights of the osteophytes averaged 4.2 mm and ranged from 1.8 to 7.8 mm ŽFig. 5.. We considered that 12 of the 24 lateral tibial plateaus had large osteophytes, which were higher than 4.2 mm. Even if the lateral tibial plateaus had large osteophytes, they had well preserved articular cartilage in 10 of 12 cases.
4. Discussion Although HTO and UKA are useful operative procedures for osteoarthritis of the knee, a major problem is the assessment of the status of the articu-
219
lar cartilage in the uninvolved compartment, as Laskin w1x already pointed out in 1978. Laskin w1x used the preoperative radiographic criteria described by Coventry: namely, no sclerosis, cystic changes, or large spurs on the uninvolved side. Gibson et al. w2x suggested the importance of stress radiography for the accurate assessment of the uninvolved compartment in degenerative arthritis of the knee when planning operative treatment. They stated that if the joint space of the uninvolved compartment on stress radiographs was 5 mm or more, the articular cartilage in that compartment should be considered normal. Kozinn et al. w3x recommended that the final decision to perform UKA had to be made after an arthrotomy had been done and the articular surfaces had been examined. In this study, we investigated the sagittal slices at the center of the lateral tibial plateaus in varus osteoarthritis by soft X-ray. Laskin w1x considered large spur formation to be a factor that indicated degenerative changes of the uninvolved compartment. However, 10 of 12 lateral tibial plateaus that had large osteophytes showed well preserved articular cartilage on soft X-rays. As the center of the lateral tibial plateau is considered to become the weight-bearing area when the knee is in valgus alignment, large osteophyte formation may not necessarily be a contra-indication to HTO or UKA. Gibson et al. w2x stated that a preserved joint space on stress radiography was a factor that indicated normal articular cartilage. Their methods could only evaluate the thickness of the articular cartilage. However, we found a bony protuberance within the articular cartilage in five of 21 cases that showed well-preserved articular cartilage. The bony protuberance can be recognized neither by stress radiography as described by Gibson et al. w2x nor by the visual appearance of the articular surface as recommended by Kozinn et al. w3x because it exists within the articular cartilage.
Fig. 5. The height of an osteophyte was defined as the distance from the subchondral plate to the top of the osteophyte.
220
T. Sugita et al. r The Knee 7 (2000) 217᎐220
Brocklehurst et al. w4x biochemically analyzed the articular cartilage from osteoarthritic and normal control adult human knee joints. They suggested that HTO or UKA might be rational procedures for knees in which the cartilage in all of one component was visually intact. Obeid et al. w5x studied the mechanical properties of cartilage from the apparently unaffected compartment of knees with unicompartmental osteoarthritis. They concluded that the apparently unaffected cartilage in knees with unicompartmental osteoarthritis was mechanically inferior to normal cartilage, even though clinically, radiologically, and morphologically it appeared to be sound. Although the mechanical and biochemical properties were not examined in our study, the existence of a bony protuberance must be a disadvantage for supporting load, because the thickness of the overlying articular cartilage is reduced by the bony protuberance. Accordingly, cases with a bony protuberance should not undergo HTO or UKA. How can the existence of a bony protuberance be determined clinically? To our knowledge, bony protuberances have been described only by Bergman et al. w7x as bone formation within the hyaline cartilage. However, they did not state whether these could be depicted on radiographs or MR imaging. We retrospectively examined conventional radiographs, tomograms, and MR imagings, but could not find bony protuberances on them. Mechanical or biochemical investigations on the articular cartilage with bony
protuberance are needed. Clinically, more detailed examinations may be necessary to disclose the bony protuberance preoperatively.
Acknowledgements The authors wish to thank Professor George Bentley for his kind advice. References w1 x w2x w3x w4x w5x w6x
w7x
Laskin RS. Unicompartmental tibiofemoral resurfacing arthroplasty. J Bone Joint Surg wAmx 1978;60-A:182᎐185. Gibson PH, Goodfellow JW. Stress radiography in degenerative arthritis of the knee. J Bone Joint Surg wBrx 1986;68B:608᎐609. Kozinn SC, Scott R. Unicondylar knee arthroplasty. J Bone Joint Surg wAmx 1989;71-A:145᎐150. Brocklehurst R, Bayliss MT, Maroudas A et al. The composition of normal and osteoarthritic articular cartilage from human knee joints. J Bone Joint Surg wAmx 1984;66-A:95᎐106. Obeid EMH, Adams MA, Newman JH. Mechanical properties of articular cartilage in knees with unicompartmental osteoarthritis. J Bone Joint Surg wBrx 1994;76-B:315᎐319. Rosenberg TD, Paulos LE, Parker RD, Coward DB, Scott SM. The forty-five-degree posteroanterior flexion weightbearing radiograph of the knee. J Bone Joint Surg wAmx 1988;70-A:1479᎐1483. Bergman AG, Willen HK, Lindstrand AL, Pettersson HTA. Osteoarthritis of the knee: correlation of subchondral MR signal abnormalities with histopathologic and radiographic features. Skeletal Radiol 1994;23:445᎐448.