Rheumatology 2001; 40: 631-639
© 2001 British Society for Rheumatology
Original Papers |
Patient-relevant outcomes fourteen years after meniscectomy: influence of type of meniscal tear and size of resection
Department of Orthopedics, Lund University Hospital, S-221 85 Lund and
1 Department of Orthopedics, Helsingborg Hospital, S-251 87 Helsingborg, Sweden
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Abstract |
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Objectives. To study long-term patient-relevant outcomes after meniscectomy, a surgical procedure associated with a high risk of knee osteoarthritis (OA). Principal objectives were to compare traumatic with degenerative meniscal tear and partial with subtotal meniscectomy.
Methods. We studied a well-defined cohort of 205 patients who had undergone isolated unilateral meniscectomy between 1983 and 1985. There was no previous knee surgery and all knees were stable. The type of meniscal tear and surgical resection was ascertained by review of medical records. Patients were followed up after 14 yr (range 12–15 yr) by self-administered questionnaires, one generic [Short Form 36 (SF-36)] and one disease-specific [Knee Injury and Osteoarthritis Outcome Score (KOOS)].
Results. In a multivariate analysis, using the Sports and Recreation Function and knee-related Quality of Life subscales of the KOOS questionnaire as dependent variables, patients with a degenerative tear scored significantly worse than individuals with a traumatic tear (P 
0.001). When we analysed unmatched subgroups and age- and sex-matched patients with degenerative or traumatic lesions, the same result was found for the knee-specific outcome (P 0.02) and SF-36 except for Social Functioning (P 0.04). There was no difference in outcome for the total cohort according to the type of resection. However, subgroup analyses showed that patients who underwent subtotal meniscectomy for a degenerative tear scored significantly worse on the knee-specific outcome than individuals who had had a partial meniscectomy for the same type of tear (P 0.02).
Conclusions. The long-term outcome of meniscal injury and surgery appears to be determined largely by the type of meniscal tear. Furthermore, our findings support the use of minimal meniscal resection in the treatment of degenerative tears. We suggest that the disease processes associated with the development of OA of the joint cartilage may also be active in the meniscus, and that a tear in a meniscus with degenerative changes might be regarded as the first sign of OA of the joint.
KEY WORDS: Meniscectomy, Osteoarthritis, Long-term outcome, Pain, Function, Meniscal tear, Traumatic, Degenerative, Partial, Subtotal.
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Introduction |
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Surgical removal of a meniscus in the knee has been performed since the second half of the nineteenth century [1], and for a long period during the next century the menisci were seen as a rather troublesome tissue. The prevailing method of treatment for meniscal tears was total meniscectomy, as this was regarded as a benign procedure. However, the long-term results of total meniscectomy are now well documented and show a high risk of functional deterioration and osteoarthritis (OA) [2–5]. The important role of the menisci in knee function and in preserving knee health has been shown in several studies [6–8]. Surgical practice is therefore increasingly aimed at minimal resection of injured tissue, preserving a stable meniscal remnant with as much function as possible. The short-term benefits of these meniscectomy procedures have been proven [9, 10]. The only prospective randomized long-term follow-up comparing partial and total meniscectomy showed better functional results of partial resection. However, it did not show better results with regard to the development of radiological OA [11].
Meniscal injury is common [12–14], and reports on the long-term prognosis of different types of meniscal tears have been contradictory [3, 15, 16]. We therefore performed a cross-sectional, retrospective cohort study to evaluate the long-term patient-relevant outcomes of surgical removal of a knee meniscus. We used a well-defined cohort of patients with stable knees and no previous knee surgery. Our primary objectives were to compare traumatic with degenerative meniscal tears and partial with subtotal meniscectomy. Secondary analyses were made to investigate the importance of age, sex, medial vs lateral meniscectomy, and open vs arthroscopic technique of surgery.
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Patients and methods |
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Patients
The Ethics Committee at the Medical Faculty of Lund University approved the study. All patients who underwent meniscectomy at Lund University Hospital between 1983 and 1985 were eligible for inclusion in the study. Individuals were identified by manually searching the surgical records at the Department of Orthopedics. The medical records of the patients were reviewed. General and knee-specific criteria for exclusion from the study are listed in Fig. 1
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Five hundred and fifty-two meniscectomies were performed on 519 patients between 1983 and 1985. The inclusion and exclusion criteria were used to identify 264 patients, who were sent two self-administered questionnaires to assess general health status, knee-specific symptoms and knee function (Fig. 1
). We obtained their current addresses through the national population records. Those who did not return the questionnaires within 1 month were sent one reminder. Fifty-three patients did not respond, which gave a response rate of 80%. Six patients were excluded after returning the questionnaire because they fulfilled one of the exclusion criteria. Thus, 205 individuals who underwent isolated unilateral meniscectomy between 1983 and 1985 were followed up in this study.
The surgical procedure was arthroscopic and/or by open arthrotomy. Twenty-three orthopaedic surgeons performed the operations. We recorded the type of meniscal tear, its location within the meniscus, the compartment affected, and cartilage and ligament status. The classification of the tears was modified after the criteria described by Newman et al. [17] (Fig. 2). We further classified longitudinal tears as traumatic, and flap tears, horizontal tears and tears in a meniscus with degenerative changes as degenerative. In epidemiological [18] and necropsy studies [12, 13], horizontal and flap tears have been described as being degenerative. There is no consensus on the origin of radial tears, and we therefore chose not to include them when comparing traumatic and degenerative tears. Joint cartilage changes noted at the time of surgery were graded as no changes, lesions without visible bone, and lesions with exposed bone. Age at onset of knee symptoms, and whether it was acute or insidious, was also recorded. If any part of the meniscus was removed, leaving a minimum of two-thirds of the meniscal surface intact, we classified the resection as partial. We considered a meniscectomy of more than one-third of the meniscal surface as subtotal. Demographic data for the cohort and findings at index surgery are presented in Table 1 .
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During the follow-up period, 21 patients from the study cohort had a reoperation on the meniscus in the index knee; in six of these patients, who had had a previous partial meniscectomy, the reoperation was a subtotal resection. All reoperations were performed within 3 yr after the original meniscectomy, and the resections were therefore regarded as subtotal. At the index surgery, two of these patients had an arthroscopic meniscectomy, but their reoperation was open and these patients were therefore described as having had open surgery. In cases in which the patient first had a diagnostic arthroscopy and the following meniscectomy was done by arthrotomy, the operation was described as open. During the follow-up, four patients had an operation on the index knee with a high tibial osteotomy for OA. Twenty-one patients had a subsequent meniscectomy in the contralateral knee, and two of these individuals later underwent tibial osteotomy. Another patient received a total knee arthroplasty of the contralateral knee. The information on subsequent surgery is based on the medical records at Lund University Hospital and self-reported information from the patients.
Questionnaires
We used the Short Form-36 item (SF-36) of the Medical Outcome Study Standard Swedish Version 1.0 [19] and the Knee Injury and Osteoarthritis Outcome Score (KOOS) Swedish Version LK 1.0 [20]. For both questionnaires a score from 0 to 100 is calculated; 100 represents the best result. In addition to the questionnaires, specific questions about possible knee problems, treatment and other joint-related disease were asked.
SF-36 is a widely used, self-administered measure of general health that assesses the following eight dimensions: Physical Functioning, Role–Physical, Bodily Pain, General Health, Vitality, Social Functioning, Role–Emotional and Mental Health [21].
KOOS is a 42-item, self-administered, knee-specific questionnaire based on the WOMAC (Western Ontario McMaster) Osteoarthritis Index [22, 23], and WOMAC scores can thus be calculated. KOOS was developed to be used for short- and long-term follow-up studies of knee injury, and the measure comprises five subscales: Pain, Symptoms, Activities of Daily Living (ADL), Sports and Recreation Function (Sports/Recreation) and knee-related Quality of Life (QOL). The measure has been shown to be valid for patients undergoing reconstruction of the anterior cruciate ligament [24] and meniscectomy [25]. We considered the KOOS to be the primary outcome measure.
Data handling, analysis and statistics
The surgical records used for the collection of data were not standardized. However, two of the authors were involved in the data extraction, and where there was uncertainty of interpretation of the records a consensus was reached. If any uncertainty remained, the data were recorded as non-classified. If a patient had left questions unanswered in any part of a questionnaire, we returned that part to the patient to be completed. The questionnaires were thus fully completed, except for a small number of the SF-36 questions; missing values were handled according to the guidelines [19]. The WOMAC scores were calculated from the KOOS questionnaire. The groups and subgroups of patients and statistical methods used in the main analyses are presented in Fig. 3. Univariate and multivariate effects, with respect to the main factors of the most affected outcome (KOOS Sports/Recreation and QOL), were subjected to analysis of variance (ANOVA). Factors with a P value of < 0.15 obtained from the univariate analysis were considered in the multivariate analysis. Three analyses (analyses 3, 5 and 7) were performed with age- and sex-matched patients, for whom we tolerated an age difference at the index operation between the paired individuals of less than 3 yr. The Wilcoxon test was used to compare matched pairs and the Mann–Whitney U-test to compare unmatched subgroups. We considered P 0.05 to indicate a significant difference.
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Results |
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Patient characteristics and multivariate analysis
Demographic data and findings at index surgery are presented for the total study cohort and two of the three pairs of subgroups with age- and sex-matched patients (Table 1
). The corresponding main parameters for non-respondents (n = 53) were as follows: female 11%, medial meniscectomy 79%, open technique of surgery 60%, partial resection 49%, mean age at index surgery 34.7 yr, and longitudinal (traumatic) meniscal tear 38%.
In the multivariate analysis (analysis 1, Fig. 3), using KOOS Sports/Recreation and QOL as dependent variables, we found a significant influence only for type of meniscal tear; patients with a degenerative tear scored significantly lower, i.e. had worse knee function and more severely affected knee-related QOL (P < 0.001) (Table 2 ).
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On the basis of these results and our primary objectives, additional statistical analyses were made. Because the mean age at surgery differed between the unmatched study groups, comparisons were also made with age- and sex-matched individuals.
Traumatic vs degenerative meniscal tear
Patients with a degenerative meniscal tear scored significantly lower on all subscales in the knee-specific outcome (P 0.007) and on SF-36 except for Social Functioning (P 0.04), compared with individuals with a traumatic tear (analysis 2, Fig. 3). The mean age at surgery was 5.3 yr greater in the subgroup with degenerative tears than in the subgroup with traumatic tears, but the female:male ratio (1:4) was the same. The differences remained on analysis with age- and gender-matched individuals (analysis 3, Fig. 3, Table 1), but were less marked. The mean score differences between the two subgroups for KOOS ranged from 6 to 18/100 points (P 0.02) (Fig. 4). The differences using WOMAC were 8 to 9/100 points (P 0.007). In SF-36 the differences remained approximately the same as for unmatched subgroups (P 0.04) (Fig. 5).
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) or degenerative (•) meniscal tear (±95% confidence interval) (analysis 3). ADL, Activities of Daily Living.
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Patients with radial and non-classified tears had scores between those of patients with traumatic tears and patients with degenerative tears (data not shown).
Partial vs subtotal meniscectomy
We found no significant differences in outcomes between these two subgroups, irrespective of whether the comparison was made between unmatched subgroups or between age- and sex-matched individuals (analyses 4 and 5, Table 1, Fig. 3). Most meniscal tears were accounted for by longitudinal (traumatic) and flap (degenerative) tears. However, they were unevenly distributed between the two subgroups. The ratio of degenerative to traumatic tears was about 2:1 in partially meniscectomized patients compared with about 1 : 2 in the corresponding group of subtotally meniscectomized individuals.
We therefore further subgrouped the patients with a degenerative tear according to the type of resection (analyses 6 and 7, Fig. 3). The differences in outcomes between patients with a degenerative tear and a partial or subtotal meniscectomy were significant; individuals who had undergone subtotal meniscectomy scored the worst. In the analysis with unmatched patients (analysis 6, Fig. 3, Table 3) this was true for the knee-specific outcome (P 0.002) and the SF-36 subscales Physical Function and Bodily Pain (P 0.03). With age- and sex-matched individuals (analysis 7, Fig. 3, Table 3), the differences remained in the knee-specific outcome (P 0.02). The mean KOOS score difference ranged from 13 to 22/100 points (P 0.02). The difference in WOMAC ranged from 14 to 17/100 points (P 0.02). No corresponding analyses were made for the traumatic tears because of the small number of patients undergoing partial meniscectomy (n = 9).
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Other factors
An analysis of unmatched subgroups showed differences in knee-specific score depending on age at index surgery. Patients over 40 yr of age at the meniscectomy scored, on average, 9 points lower on the Activities of Daily Living subscale of the KOOS (P = 0.008) and 10 points lower on Sports/Recreation (P = 0.07) than patients below 30 yr of age at surgery. The ratios of degenerative to traumatic tears were 1.2:1 and 1:2.3 respectively. Females had lower mean scores on all subscales of the knee-specific outcome when compared with males in the corresponding subgroups, but the differences were not significant [P = 0.08 in the multivariate analysis (analysis 1, Fig. 3, Table 2) for the KOOS subscales Sports/Recreation and QOL]. The proportions of traumatic and degenerative meniscal tears were about equal in males and females, and mean age at index surgery differed by only 0.4 yr. No significant differences in outcome were seen whether the meniscectomy was performed by arthrotomy or by arthroscopy, whether the lesion was on the medial or lateral meniscus, or whether the onset of symptoms was acute or insidious.
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Discussion |
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TopAbstractIntroductionPatients and methodsResultsDiscussionReferences |
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Principal findings and definitions
Our main objectives were to assess the long-term patient-relevant outcomes of meniscectomy, and to compare traumatic with degenerative meniscal tears and partial with subtotal meniscectomy. We found a significantly worse outcome in patients with a degenerative tear than in patients with a traumatic lesion. Furthermore, patients with a degenerative tear that had undergone subtotal meniscectomy had a worse long-term outcome than those with the same injury treated by partial meniscectomy.
The terms ‘traumatic meniscal tear’, ‘degenerative meniscal tear’, ‘partial meniscal resection’ and ‘subtotal meniscal resection’ are used in the clinic and in research. Our classification of traumatic and degenerative meniscal tears is based on morphology and is supported by previous studies [12, 13, 18]. This classification does not necessarily correlate with the patient's onset of symptoms. Thus, a degenerative tear resulting from a minor trauma may present with acute symptoms. Partial meniscectomy has traditionally been described as resection of the injured region of the meniscus only, preserving a stable remnant. Total meniscectomy, rarely used today, is carried out along the transitional zone between the meniscus and the joint capsule and preserves only a small rim. We used a definition based on the proportion of meniscal tissue excised and we set the criterion for partial resection as the removal of one-third or less of the cartilage-covering meniscal surface.
Strengths and limitations of the study
We performed a long-term follow-up of a large, well-defined cohort of patients with no previous knee injuries, with a reply frequency of 80% and a narrow range of follow-up times. Individuals with other possible confounding joint-related disease or major ligament injury on any knee before or after index surgery were excluded. Patients who, after index surgery, underwent further meniscectomies or OA-related surgery on any knee were included, because exclusion of these individuals would have resulted in selection for patients without predisposition to OA.
The construction, score aggregation, mode of administration and validity of the measures used in most outcome studies of meniscectomy have been questioned [26–28]. Data regarding symptoms and function have been collected by interview, with bias being introduced by the observer [29, 30]. The use of self-administered outcome measures is now promoted [31, 32], and a conceptual framework for outcomes research in arthroscopic meniscectomy has been published, emphasizing the use of patient-relevant outcomes such as the ability to walk, do housework or be active in sports rather than measures of physical impairment (range of motion, effusion, etc.) [33]. We considered KOOS to be the primary outcome measure. This measure was developed to evaluate the patient's perspective of knee injury and knee OA, and it includes two subscales (Sports/Recreation and QOL) that are more sensitive than the WOMAC in younger or physically active individuals with post-traumatic OA [34].
This study was retrospective, with the associated weaknesses. Twenty-three surgeons performed the meniscectomies at the same clinic. The surgical procedure was done in most cases by arthrotomy because the arthroscopic technique at Lund University Hospital was still in an early phase. The type and location of the meniscal tear, the amount of tissue removed and joint cartilage status were occasionally difficult to determine from the surgical reports. Cases in which the documentation was insufficient for determination were labelled as non-classified. No adjustments were made for workload and body mass index because of insufficient data.
Traumatic vs degenerative meniscal tear
The relatively poor outcome for degenerative meniscal tears is consistent with our earlier findings that degenerative tears were more often associated with advanced OA at follow-up [15]. Furthermore, a follow-up of arthroscopic meniscectomies (mean 8.5 yr) suggested worse functional outcome in patients with flap and horizontal tears than in patients with bucket-handle tears, although the differences were not significant except for pain after exercise [35]. In contrast, other studies have failed to show a difference in long-term outcome due to the type of meniscal tear [3, 16]. Comparison of our results with these studies is confounded, however, by their inclusion of patients with total meniscectomy and small patient numbers. Neyret et al. [36] reported that two distinct populations required OA surgery after meniscectomy. One group was young with a long delay to OA surgery (mean 26 yr), and one group was older with a shorter delay (mean 9.8 yr). The authors indicated that the proportion of degenerative tears was higher in the older age group. Our study confirms that a relatively high proportion of younger patients undergo meniscectomy for traumatic tears in normal menisci, whereas older patients more often undergo meniscectomy for tears in menisci that are already undergoing age-related and degenerative changes [15, 18, 37]. Such changes may predispose the meniscus to tear, either spontaneously or by minor trauma.
Partial vs subtotal meniscectomy
Our results showed no significant differences in long-term outcomes when we assessed the total study cohort with regard to the type of meniscal resection. However, a typical longitudinal (traumatic) tear, leading to resection of the anterior, middle and posterior parts of the meniscus, was generally followed by subtotal resection. The counterpart, a degenerative tear, more often led to partial resection. Consequently, the proportion of traumatic and degenerative tears differed between these two study groups. Because of the small number of longitudinal tears treated with partial meniscectomy, it was possible to perform a subgroup analysis only for the degenerative tears. This subanalysis showed that patients who underwent partial meniscectomy for a degenerative tear had a better long-term outcome than patients who underwent more extensive resection for a similar type of tear. These results corroborate previous findings suggesting that the amount of meniscal tissue excised is inversely related to the function of the knee at long-term follow-up [38, 39].
General discussion
On the basis of the results of the present and previous studies, we hypothesize that a tear in a meniscus with degenerative changes is often associated with pre-existing structural changes in the articular cartilage that may represent early-stage OA. The cartilage changes may or may not be visible at arthroscopy. Such a joint cartilage would be less able to withstand the increased load associated with the removal of a load-bearing portion of the meniscus and would be highly prone to the development of OA. This would be consistent with the worse long-term outcome of degenerative tears compared with traumatic tears.
We further suggest that the same disease processes that are associated with the development of OA of the joint cartilage may be active in the meniscus, and that a tear in a meniscus with degenerative changes might thus be regarded as a first sign of OA of that joint. This would be in line with the view that OA is a disease of the joint, not only the joint cartilage.
There may be several explanations of our finding that a more extensive meniscal resection of a degenerative meniscal tear was associated with a worse outcome at follow-up compared with a smaller resection. First, further loss of meniscal tissue may accelerate the development of OA through increased contact stress on the articular cartilage [6–8]. Secondly, for patients with subtotal resections, the meniscal degeneration and tears may have been more extensive and the changes in the joint cartilage may already have been more advanced at index surgery than in those in whom only a partial resection was made. We found no evidence for worse cartilage status at surgery in the former group. However, the difficulty of detecting and classifying early cartilage changes, combined with insufficient reporting, limits the weight of the evidence.
Our findings support the use of minimal meniscal resection in the treatment of degenerative tears. However, we cannot conclude from these results whether this is also true for traumatic tears. The question of whether a stable degenerative tear should be excised cannot be answered at present. However, there is little evidence that leaving these tears increases the risk of OA compared with resection [40]. The clinical decision in the individual case is confounded by the difficulty of discriminating between the symptoms caused by a tear in the degenerated meniscus and those caused by early-stage OA. Further prospective studies using a combination of patient-relevant outcomes, radiology and biomarkers are needed to explore the long-term consequences of meniscal injury and surgery with regard to the development of OA [41].
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Acknowledgments |
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This study was supported by grants from the Swedish Rheumatism Association, The Swedish Foundation for Health Care Sciences and Allergy Research, The Swedish National Centre for Research in Sports, The Swedish Medical Research Council and Lund University Hospital and Medical Faculty.
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Notes |
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Correspondence to: S. Lohmander.
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