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© 1997 The Journal of Bone and Joint Surgery, Inc. Total Knee Replacement in Young, Active Patients. Long-Term Follow-up and Functional Outcome*  , NEW YORK, N.Y.Investigation performed at the Insall-Scott-Kelly Institute for Orthopaedics and Sports Medicine, Beth Israel North Medical Center, New York City
We reviewed our experience with total knee arthroplasties performed between 1977 and 1992 in patients who were fifty-five years old or less to determine the appropriate management for younger patients who have severe osteoarthrosis. One hundred and fourteen knee replacements were performed in eighty-eight patients who were an average of fifty-one years old (range, twenty-two to fifty-five years old). All of the operations were performed by one of the two senior ones of us (J. N. I. or W. N. S.) with the use of cementing techniques. A posterior stabilized, posterior cruciate-substituting design was used for all but one replacement, for which a semiconstrained total condylar prosthesis was used. Six knees (four patients) were lost to follow-up. Follow-up data for the remaining 108 knees (eighty-four patients) were used to perform the survivorship analysis. One hundred and three unrevised knees (eighty patients) were available for clinical evaluation with the scoring systems of The Hospital for Special Surgery and the Knee Society at an average of eight years (range, three to eighteen years) postoperatively; thirty-six knees were followed for more than ten years. In addition, the activity levels of the patients were assessed with the activity score of Tegner and Lysholm. Radiographs were examined for evidence of loosening of the component. At the latest follow-up examination, the average knee score according to the system of The Hospital for Special Surgery had improved from 55 points preoperatively to 92 points. According to the system of the Knee Society, the average knee score was 94 points and the average functional score was 89 points. The result for all 103 knees was good or excellent according to the knee scores of The Hospital for Special Surgery and the Knee Society. Ninety-seven knees (94 per cent) had good or excellent function according to the functional score of the Knee Society. The average activity score of Tegner and Lysholm improved from 1.3 points (range, 0 to 4 points) preoperatively to 3.5 points (range, 1 to 6 points) at the latest follow-up examination. All but two patients had improvement in the activity score postoperatively, and nineteen (24 per cent) of the eighty patients had an activity score of at least 5 points, indicating regular participation in activities such as tennis, skiing, bicycling, or strenuous farm or construction work. Nine (9 per cent) of the 103 knees had non-progressive tibial radiolucent lines. Two patients had a revision because of late infection, and one patient had revision of a well fixed tibial component because of wear of the polyethylene. In addition, three patellar components were revised for loosening, and one spacer was exchanged to treat instability. With failure defined as revision of either the femoral or the tibial component, the over-all rate of survival was 94 per cent at eighteen years. When the three patellar revisions were included in the failures, the survival rate was 90 per cent at eighteen years. When the exchange of the spacer was also included in the failures, the survival rate was 87 per cent at eighteen years. We consider arthroplasty with cementing of a posterior stabilized total knee prosthesis to be effective operative treatment with durable results for osteoarthrosis in younger patients when other, less invasive measures have failed. Within the average eight-year follow-up interval of this study, polyethylene wear, osteolysis, and loosening of the conforming posterior cruciate-substituting prosthesis were not major problems for these younger, active patients, although it is possible that this observation could change with an even longer duration of follow-up.
A painful osteoarthrotic knee in a young patient presents a therapeutic dilemma48. Non-operative modalities, such as physical therapy, modification of activities to limit those that involve impact, and anti-inflammatory medications, often provide only limited and temporary benefit. Operative options include arthroscopic débridement, arthrodesis, proximal tibial osteotomy, and unicompartmental or total knee replacement. Few patients are willing to accept the functional limitations imposed by an arthrodesis of the knee. Proximal tibial or distal femoral osteotomy, while permitting unrestricted activity and good short-term results, does not predictably relieve pain over the long term10,33,40,51. Unicompartmental knee replacement offers an alternative for patients who have varus angulation of the knee and osteoarthrosis of the medial compartment, but often degenerative changes are not limited to one compartment30,34,45. Knee replacement has been shown to offer predictable pain relief with improved function in elderly patients or patients who have rheumatoid arthritis8,13,16,20,22,25. Total knee replacement has been shown to be effective in younger patients as well12,18,46,47, but there is concern regarding the possibility of aseptic loosening due to wear debris generated by a younger, active patient over many years5,14,27,55. Because of the potential for numerous revision operations in the course of a lifetime, total knee replacement has generally been reserved for patients who are at least sixty years old23,39. However, we are not aware of any study in which the activities of patients after a knee replacement were specifically examined to determine if any are, in fact, associated with increased loosening. Similarly, we know of no study that has documented whether there is increased loosening of total knee replacements over the long term in younger patients who have osteoarthrosis. The purpose of the present study was to determine the clinical, radiographic, and functional results of total knee replacement for osteoarthrosis or post-traumatic osteoarthrosis in patients who were fifty-five years old or less at the time of the arthroplasty. Also, to assess better the functional outcome after total knee replacement in younger patients, we examined the specific activities in which the patients participated.
Between 1977 and 1992, the two senior ones of us (J. N. I. and W. N. S.) performed 114 primary total knee replacements in eighty-eight patients who were fifty-five years old or less. Two patients died, at seven and thirteen years postoperatively; it was confirmed that the prostheses were functioning well and were intact at the time of death. Two patients, one of whom had an intact contralateral knee replacement, had a successful two-stage reimplantation to treat late infection. Another patient had aseptic revision of the tibial component at seven years because of polyethylene wear. Only four patients (six knees) were lost to follow-up. Thus, follow-up and survivorship information was available for 108 (95 per cent) of the 114 knees in eighty-four (95 per cent) of the eighty-eight patients. One hundred and three unrevised knees (eighty patients) were available for clinical evaluation at an average of eight years (range, three to eighteen years) postoperatively. The average age of the patients at the time of the knee replacement was fifty-one years (range, twenty-two to fifty-five years). There were twenty-nine men (35 per cent) and fifty-five women (65 per cent). Fifty-four right knees (50 per cent) and fifty-four left knees were included in the study. Patients who had rheumatoid arthritis or another inflammatory arthropathy were excluded from the study. The diagnosis was primary osteoarthrosis for sixty-nine knees (64 per cent) and post-traumatic osteoarthrosis for thirty-nine knees (36 per cent). Six of the knees affected by post-traumatic osteoarthrosis had been previously affected by septic arthritis, which had been treated successfully. Sixty-three knees (58 per cent) had a total of 135 operative procedures before the knee replacement, for an average of 2.1 procedures (range, one to fourteen procedures) per knee. All knee replacements were performed with the use of cementing techniques. All but one of the prostheses were posterior stabilized, posterior cruciate-substituting designs. The remaining knee replacement was a posterior cruciate-sacrificing semiconstrained total condylar design that was used before the cruciate-substituting versions were available. Fifteen prostheses had an all-polyethylene tibial component, and ten had a component with an augmented stem extension, including six with a semiconstrained polyethylene spacer for ligamentous instability (constrained condylar design). The average thickness of the 108 polyethylene spacers was 10.3 millimeters (range, 7.5 to 25.0 millimeters), with seventy-eight (72 per cent) of the spacers being at least ten millimeters thick. Patellar resurfacing was performed routinely and was done with an all-polyethylene component inserted with cement in all but five knees, in which a metal-backed patella was implanted with cement. Twenty patients had concurrent bilateral knee replacement, and four patients had a staged bilateral procedure. Three additional patients had the contralateral knee replaced after the age of fifty-five years. Although that arthroplasty was not included in this study, those patients had a bilateral replacement when they were assessed for function at the latest follow-up examination. Therefore, a total of twenty-seven patients had a bilateral knee replacement when evaluated for the level of activity at the latest follow-up examination.
Clinical Evaluation
Radiographic Evaluation
Survivorship Analysis
Clinical Results
Activity Score The subset of twenty-seven patients who had bilateral knee replacement had similar improvement in the activity score of Tegner and Lysholm49, from an average of 1.1 points (range, 0 to 3 points) preoperatively to an average of 3.3 points (range, 2 to 6 points) at the latest follow-up examination. Two patients who had a bilateral knee replacement had a postoperative activity score of 6 points, indicating regular participation in downhill skiing or tennis. Thus, bilateral knee replacement in younger patients permitted an increase in the level of activity that was comparable with that for the entire group. Many patients were quite active despite the usual cautions to avoid activities involving impact after total knee replacement. Nearly one-fourth (nineteen) of the eighty patients had an activity score of 5 or 6 points at the latest follow-up examination, indicating participation in strenuous farm or construction work and competitive cycling or cross-country skiing (a score of 5 points) or participation in tennis or downhill skiing (a score of 6 points). Regular walking for exercise, for a distance of two miles (3.2 kilometers) a day for example, was the most common activity (forty-eight patients, 60 per cent). Use of either a stationary or a conventional bicycle was the second most common activity (forty-two patients, 53 per cent). Other activities included golf (nineteen patients, 24 per cent) and use of a treadmill for exercise (sixteen patients, 20 per cent). Seven patients performed aerobics, nine played tennis, ten used a stair-climbing machine, thirteen hiked or hunted, nine performed construction or farm work, and six participated in downhill skiing. Eight patients (10 per cent) had been unable to work preoperatively specifically because of the knee (an activity score of 0 points); five of these patients were able to return to work postoperatively and remained employed at the time of the latest follow-up examination.
Radiographic Results There were no other instances of radiographic loosening or osteolysis. Specifically, no changes were noted in the alignment or position of the prosthesis other than that in the patient just described. Also, excluding the components that were revised, there was no gross evidence of thinning or asymmetry consistent with wear of the polyethylene or failure of the tibial spacer or the patellar component.
Revisions One patient, who was the youngest patient (twenty-two years old) at the time of the knee replacement, had revision of a well fixed tibial component in an aseptic joint. Before the total knee arthroplasty, the patient had had fourteen operations on the knee, including three attempted reconstructions of the anterior cruciate and medial collateral ligaments and multiple débridements for septic arthritis after a wound infection. After the total knee replacement, the patient regularly participated in impact and contact sports, such as football, basketball, and softball, and was employed as a firefighter. This patient was the only one to have an activity score49 of 7 points during the follow-up period. Recurrent effusions began to develop seven years postoperatively; examination of aspirated joint fluid revealed polyethylene wear debris. The wear was confirmed with arthroscopy, and the tibial component was revised to a newer version that would allow exchange of the polyethylene spacer in the future. Despite the wear of the polyethylene, the tibial tray was well fixed. The initial tibial component had been an endoskeleton metal-backed type with a 7.5-millimeter carbon-fiber-reinforced polyethylene spacer. After the revision, which was performed four years before the latest follow-up examination, the patient resumed cycling, golf, and cross-country skiing without problems. Three patients had revision of the patellar component only; two of the three components were metal-backed2,3. These knees continued to function well and were included in the series. Another patient had arthroscopic débridement because of a so-called clunk, impinging soft tissue under the patella, at four years without revision of the components22. The result of the replacement in this patient was not considered a failure in the survivorship analysis.
Dislocations
Survivorship Analysis
When the three isolated patellar revisions were included as failures, the rate of survival was 90 per cent at eighteen years. When any operative intervention that altered the knee component (the exchange of a spacer because of instability) was included, the rate of survival at eighteen years was 87 per cent.
Total knee replacement in elderly patients has been well documented as effective for relief of pain, correction of deformity, and improvement of function8,13,16,20,22,25. However, concerns about potential loosening and the need for multiple revisions have discouraged the widespread use of total knee arthroplasty in younger patients who have osteoarthrosis. In the present study, we examined the long-term functional outcome of knee replacements in younger patients, with special attention to activities in which the patients participated, regardless of the recommendations of the surgeon. We also examined the long-term survival of knee replacements in younger, active patients to determine if they were as successful as those in older patients32,37-39,43,53. As far as we know, we are reporting the results of the longest follow-up of the largest series of total knee arthroplasties performed for osteoarthrosis or post-traumatic osteoarthrosis in a younger population. Stern et al. demonstrated similar clinical results during a six-year follow-up of a smaller group of total knee arthroplasties performed for osteoarthrosis46. The present study incorporates and expands on a subset of those patients46 who had the operation performed by the senior one of us (J. N. I.), includes a longer period of follow-up, and provides an assessment of the activity levels of the patients. Other studies of young patients who had a knee replacement have included patients who had rheumatoid arthritis and relatively few patients who had osteoarthrosis, and the periods of follow-up have been shorter11,12,18,47. To our knowledge, no other investigator has used a rating system such as the activity score of Tegner and Lysholm49 to quantify the activity levels and participation in sports of this patient population. Our clinical results are similar to those in published reports on older patients8,13,16,20,22,25, although such historical comparisons may not be valid. All of the knee and functional scores according to the systems of The Hospital for Special Surgery and the Knee Society for the category-A and B patients (sixty-nine knees) were good or excellent. All of the knee scores and twenty-eight (82 per cent) of the functional scores for the category-C patients (thirty-four knees) were good or excellent. Functional improvement was assessed further with use of the activity score of Tegner and Lysholm49. All but two patients, who had no change in the score, had an improved activity score at the latest follow-up examination compared with the preoperative score. Additionally, nineteen patients (24 per cent) had a score of at least 5 points, indicating regular participation in activities such as tennis, downhill skiing, cycling, or strenuous farm or construction work. Despite the patients' active lifestyles, loosening that necessitated revision was not a notable problem in this series. The survivorship estimate, with revision of the femoral or tibial component as the end point, was 94 per cent at eighteen years. Two patients who had a late infection due to a traumatic injury had a successful two-stage reimplantation. The only aseptic revision involved the youngest patient, who participated in football, basketball, and softball and was employed as a firefighter. The revision, seven years postoperatively, revealed wear of a relatively thin, carbon-fiber-reinforced polyethylene spacer without loosening of the tibial tray. Accelerated wear of carbon-fiber-reinforced polyethylene has been well documented, and this material is no longer recommended for use in knee replacements52,57. Several factors may have contributed to the excellent rate of survival of the prostheses in these younger, active patients. Thicker polyethylene spacers have been shown to decrease wear7,56. The average thickness of the tibial polyethylene was 10.3 millimeters, seventy-eight (72 per cent) of the 108 spacers were at least ten millimeters thick, and no spacer was less than 7.5 millimeters thick. The relatively conforming geometry of the articulating surfaces of the posterior stabilized prosthesis helps to reduce contact stresses and may reduce wear of the polyethylene, especially when compared with other, flat-on-flat designs5,14,29,42,44. Cement fixation has also been shown to be an effective barrier against penetration of polyethylene particulate debris, which may result in aseptic loosening6,27,29,52. Additionally, attention to alignment of the prosthesis as well as to soft-tissue and ligament balancing by an experienced surgeon may help to avoid eccentric loading and shear14,29,55. The present study was of results obtained by experienced surgeons in a practice that deals almost exclusively with problems related to the knee. Outcomes may vary for surgeons who perform total knee replacements only occasionally. Also, the results of this study should not be extrapolated to techniques that involve insertion without cement or to all knee-replacement designs. Operative options available for a younger patient with osteoarthrosis in whom non-operative treatment has failed include arthroscopic débridement, osteotomy, unicompartmental knee arthroplasty, total knee replacement, and arthrodesis of the knee. Few patients are willing to accept the functional limitations of an arthrodesis. Arthroscopic débridement is unpredictable for relief of pain, and improvement is often temporary because the underlying arthritic process is not altered4,41,50. Proximal tibial or distal femoral osteotomy traditionally has been recommended for the younger age-group. Unicompartmental pain and early osteoarthrosis as a result of malalignment of the mechanical axis can be treated with osteotomy about the knee with good short-term results9,31,33,40. However, several studies have demonstrated that results deteriorate with time10,35,51. In a study by one of us and colleagues, eighty-one (85 per cent) of ninety-five knees had a good or excellent result at five years postoperatively, compared with only sixty (63 per cent) at ten years21. Coventry found that only twenty-one (62 per cent) of thirty-four knees had less pain and only twenty-two (65 per cent) had better function at ten years9. Nagle et al.35 and Holden et al.17 also found that a proximal tibial osteotomy, at best, allows a patient to sustain the preoperative level of activity and that the level usually decreases with time. Additionally, revision of a proximal tibial osteotomy to a total knee replacement may yield results similar to those of revision total knee replacement15,28,54. Factors such as patella infera, previous incisions, lack of sufficient tibial bone stock, altered anatomy, and existing hardware make knee replacement after an osteotomy more demanding19,54. Similarly, revision of a unicompartmental arthroplasty of the knee to a total replacement of the knee can be a technically difficult procedure1,34,36. The narrow operative indications often preclude use of the unicompartmental arthroplasty in a younger patient who has osteoarthrosis or post-traumatic osteoarthrosis of the knee. The ideal patient is one who places low demands on the knee; is thin; and has good preoperative motion, no patellofemoral symptoms, little deformity, and osteoarthrosis limited to one compartment30,45. None of the younger, active patients in the present study who had osteoarthrosis involving multiple compartments would have been an appropriate candidate for unicompartmental replacement. Concerns about wear debris and loosening over the long term after unicompartmental arthroplasty are the same as those after total knee arthroplasty. No long-term study of which we are aware has demonstrated a rate of survival of the femoral and tibial components of total knee replacements in any age-group that has approached the 94 per cent rate at eighteen years that we report here30,34. We believe that insertion of a posterior stabilized knee replacement with cement is an acceptable option for younger patients who have osteoarthrosis that has not responded to non-operative treatment, although we realize that longer follow-up could alter our conclusions. The good results notwithstanding, common sense suggests that, until additional information is available, total knee arthroplasty in younger patients should continue to be considered with caution and activities that involve impact should be avoided. For some younger patients, deferment of definitive operative treatment may be the best option.
*One or more of the authors have received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this article. In addition, benefits have been or will be directed to a research fund or foundation, educational institution, or other non-profit organization with which one or more of the authors are associated. No funds were received in support of this study.
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