Abstract
Purpose
Total Knee Arthroplasty (TKA) is one of the most successful operations in orthopedics. Still, a sizable percentage of patients (20%) remain dissatisfied after a well-executed TKA. The study aims to examine the excised synovium from the suprapatellar region in osteoarthritic knees during TKA and evaluate the histopathology (HP) report to know whether discrepant diagnoses affect the Forgotten Joint Score-12 at various time intervals.
Methods
This is a prospective cohort study. Two hundred (160 female; 40 male) end-stage osteoarthritis patients who underwent primary TKA were studied. An inclusion criterion was patient with end-stage osteoarthritis. Clinically and serologically proven rheumatoid arthritis patients were excluded from the study. The synovium excised during the TKA procedure was sent for the HP examination. The statistical significance was measured with the Chi-square test and two-sample t-test.
Results
A total of 184 out of the 200 patients (92%) knee synovium showed HP features of osteoarthritis. The discordant diagnoses and discrepant diagnosis rate was 8% and 7%, respectively, which is statistically significant by Chi-square test (p value < 0.0001 and p value = 0.0001). 14 of the patients (12 F:2 M) showed histological features of inflammatory/rheumatoid arthritis who were treated, two patients (all female) showed HP features of villonodular synovitis. The mean (SD) improvement in FJS-12 at six weeks in the concordant group (25.3 [17.6]) is significantly more than the discrepant group (15.3 [12.5]), p-value 0.0385.
Conclusion
8% of our patients exhibited unexpected results. The study showed a 7% rate of discrepant diagnosis. This discrepant diagnosis if missed and untreated, would have affected the function and long-term survival of the implanted TKA.
Keywords: Total knee arthroplasty, Histopathology examination, Discordant diagnosis, Discrepant diagnosis, Unhappy patient
1. Introduction
The Total Knee Arthroplasty (TKA) is one of the most successful operations in orthopedics. TKA is highly effective in pain relief and improves function, including daily living.1, 2, 3, 4 Bourne et al.5 have shown that a sizable percentage (19%) of patients remain dissatisfied after TKA surgery. Tremendous advances have been made in the implant designs, refinement of the surgical treatment of TKA, and patient selection. Still, various studies show only 82–89% of patients are satisfied with their primary total knee replacement.6, 7, 8, 9, 10, 11 These studies show that TKR is not achieving its goal of relieving pain and restoration of function in a substantial proportion of patients. The forgotten knee is the terminology used to describe a post TKR patient entirely unaware of his knee implant. Various factors like age, sex, BMI, preoperative pain, and preoperative patella symptoms have been studied to see their effect relationship on the achievement of forgotten knee status. All the published data to date shows no consensus in the relationship between the two. Much research is being done worldwide to identify the causes of these dissatisfied patients who otherwise have a well-executed TKA operation. Given certain studies conducted about a decade ago,12, 13, 14, 15, 16, 17 most world centers do not send the specimen, mainly synovium, during a routine TKA operation for advanced osteoarthritis. By not subjecting the tissue for histopathological (HP) examination, there is a small but definite possibility that significant pathology might be missed in a few cases. This, in turn, may affect the function and survivorship of the implanted joint.
Hence the objective of the study was to examine the excised synovium from the suprapatellar region in all osteoarthritic knees during TKA operation and evaluate the HP report to know whether discrepant diagnosis affects the Forgotten Joint Score-12 at various time intervals.
2. Materials and methods
This was a prospective study. Two hundred patients who underwent primary TKA between October 2014 and September 2016 were studied after obtaining local Ethics committee approval and obtaining consent from the patients. The synovium excised during the TKA procedure was sent for the HP examination. The synovium was removed from the suprapatellar pouch, medial and lateral gutters. The sample was checked by two fellowships trained histopathologist with aggregate clinical experience in bone pathology of 52 years.
One fellowship-trained orthopedic histopathologist’s diagnosis was checked for agreement with the diagnosis of another fellowship-trained orthopedic histopathologist. The histopathology results were categorized into three groups. (i) Concordant diagnosis, when the histopathology report matched the preoperative clinical diagnosis of osteoarthritis. (ii) Discordant diagnosis, when the histopathology report did not match the preoperative clinical diagnosis (rheumatoid arthritis and pigmented villonodular synovitis). (iii) Discrepant diagnosis when the histopathology report did not match the preoperative clinical diagnosis and is expected to alter patient management, i.e., rheumatoid arthritis. Thus, discrepant diagnosis is a part of the discordant diagnosis. Inclusion criteria were patients with the end-stage osteoarthritic knee (grade 4, bone on the bone disease) undergoing TKA. Patients who were clinically, serologically and radiologically diagnosed as rheumatoid arthritis or seronegative arthritis were excluded. One hundred sixty patients were female with a mean age of 67 years; forty were male with a mean age of 71 (Table 1). A single surgeon and assistant operated all the patients. A standard parapatellar approach was made in all the patients; TKA was performed in a standard fashion with a tourniquet. All the patients received standard pre and postoperative antibiotic prophylaxis. All patients received a cemented posterior stabilized knee implant (Freedom Total Knee system manufactured by Maxx Orthopedics Inc, PA, USA). The knee function outcome was measured with Forgotten joint score −12 (FJS-12) preoperatively two weeks before the operation, at six weeks, and at 12 months after the TKA.
Table 1.
Demography of patient population n = 200.
| Gender | Number | Age range | Mean age |
|---|---|---|---|
| Female | 160 | 58–76 | 67 |
| Male | 40 | 65–82 | 71 |
2.1. Statistical methods
The sample size was estimated to be 193 with an alpha error of 0.05 and a beta error of 0.05, with 95% power. Considering dropouts, the figure was rounded to 200. The study was started with a null hypothesis that is no difference exists between clinical and histological diagnoses. The statistical significance between concordant and discordant/discrepant diagnoses was measured with the Chi-square test, degree of freedom (DF) = 1. P value < 0.05 was considered significant. The statistical significance of FJS-12 at various time intervals was measured with a two-sample t-test. P value < 0.05 was considered significant.
3. Results
184 of the 200 patients (92%) knee synovium showed HP features of osteoarthritis (Fig. 2). The concordance rate was 92%. We found abnormal reports in 16 of our 200 knees (8%). Fourteen of these (12 females and two males) showed histological features of inflammatory/rheumatoid arthritis (Fig. 1); two patients (all female) showed HP features of pigmented villonodular synovitis (Fig. 3). Thus, the discordant diagnosis rate was 8%, and the discrepant diagnosis rate was 7% (Table 2 &Table 3). This is because discrepant diagnosis % (rheumatoid arthritis) is a part of discordant diagnosis % (rheumatoid arthritis + pigmented villonodular synovitis). The discrepant diagnosis patients whose synovium showed inflammatory/Rheumatoid arthritis features were referred to the Rheumatology consultant. The patients whose synovium showed the features of rheumatoid arthritis were treated by rheumatologist with disease modifying anti rheumatic drugs with every two monthly clinical follow up. The patients whose synovium had shown features of pigmented villonodular synovitis (PVNS) did not require any further treatment after the TKR procedure. The combined discordant diagnosis p value < 0.0001 and discrepant diagnosis p value = 0.0001 is statistically significant by the Chi-square test, Degree of Freedom = 1. Also, in the female population, the discordant diagnosis p-value = 0.0001 and discrepant diagnosis p-value = 0.0004 is statistically significant. The male population discordant and discrepant diagnosis rate of 5% versus anticipated 0% is not statistically significant (p value = 0.1547); (Table 4). The FJS-12 score improvement is substantial at one-year post TKR compared to preoperative FJS-12 scores in both the concordant and the discrepant diagnoses group (p value < 0.05). The Improvement in FJS-12 at six weeks in the concordant group (mean 25.3 and SD 17.6) is significantly more than the discrepant group (mean 15.3 and SD 12.5), which is statistically significant, p-value 0.0385. The FJS -12 score comparison between the concordant diagnoses and discrepant diagnoses group before the TKR operation and at 1-year post TKR interval is not statistically significant, with the p-value of 0.9493 and 0.9144, respectively (Table 5).
Fig. 2.
Osteoarthritis:Section shows degenerated bony fragments surrounded by inflammation and villous hyperplasia of synovium (H & E stain, 40X).
Fig. 1.
Rheumatoid arthritis:Section shows dense lymphoid aggregates beneath a hyperplastic synovial lining (H & E stain, 40X).
Fig. 3.
Pigmented villonodular synovitis:Section shows hyperplastic synovium with pigment laden macropages, inflammatory cells and giant cells (H E stain, 40X).
Table 2.
Comparison of clinical to histopathological diagnosis, 200 total knee replacements, 2014 to 2016.
| Gender | Clinical diagnosis | DJD | Histopathological Diagnosis |
|
|---|---|---|---|---|
| Inflamatory arthritis/RA | PVNS | |||
| Female | DJD 160 | 146 | 12 | 2 |
| Male | DJD 40 | 38 | 2 | 0 |
DJD: Degenerative joint disease.
RA: Rheumatoid arthritis.
PVNS: Pigmented villonodular synovitis.
Table 3.
Concordant, discordant and discrepant diagnosis.
| Gender | Total number | Concordant diagnosis | Discordant diagnosis | Discrepant diagnosis |
|---|---|---|---|---|
| Female | 160 | 146 | 14 | 12 |
| Male | 40 | 38 | 2 | 2 |
Table 4.
% of Discordant and discrepant diagnosis statistical analysis.
| Percentage | 95% CI | Chi-squared | Degree of Freedom | p value | |
|---|---|---|---|---|---|
| Female discordant diagnosis | 8.75 | 4.5652 to14.1506 | 14.595 | 1 | p-0.0001 |
| Female discrepant diagnoses | 7.5 | 3.5669 to 12.6508 | 12.429 | 1 | P = 0.0004 |
| Male discordant diagnosis | 5 | −4.4797 to 16.5039 | 2.026 | 1 | P = 0.1547 |
| Male discrepant diagnosis | 5 | −4.4797 to 16.5039 | 2.026 | 1 | P = 0.1547 |
| Combined discordant diagnosis | 8 | 4.4437 to 12.5989 | 16.625 | 1 | P < 0.0001 |
| Combined discrepant diagnosis | 7 | 3.6375%to 11.4055 | 14.472 | 1 | P = 0.0001 |
Table 5.
Forgotten Joint Score −12 at various time intervals.
| Time Interval | Concordant Diagnoses n = 184 | Discrepant Diagnoses n = 14 | P value |
|---|---|---|---|
| Pre Operative | 11.9 ± 11.4 | 11.7 ± 10.4 | P = 0.9493 |
| At 6 weeks after TKR | 25.3 ± 17.6 | 15.3 ± 12.5 | P = 0.0385 |
| At 1 year after TKR | 49.1 ± 30.2 | 48.2 ± 29.5 | p = 0.9144 |
4. Discussion
The goal of TKA surgery is to have a completely satisfied patient after the surgical procedure. Every Orthopedic surgeon wants his patient to achieve complete relief of pain and restoration of all the activities after the TKA operation. TKA is one of the most successful surgical procedures in modern-day orthopedics, reaching past 95% in situ survival over 15–20 years.18 The long-term success of TKA is remarkable and widely acknowledged. However, long-term survival is not the same for the different conditions for which TKA is used. It is shown that the implant survival rates in patients with inflammatory arthritis are less than those for uncomplicated degenerative osteoarthritis disease for several reasons.19,20 Bourne et al.5 have shown that a sizable percentage (19%) of patients remain dissatisfied after TKA surgery. Tremendous advances have been made in the implant designs, refinement of the surgical treatment of TKR, and patient selection. Still, various studies show that only 82–89% of patients are satisfied with their primary TKA.6, 7, 8, 9, 10, 11 These studies show that TKA is not achieving its goal of relieving pain and restoration of function in a substantial proportion of patients. The forgotten knee is the terminology used to describe a post TKA patient entirely unaware of his knee implant. Various factors like age, sex, BMI, preoperative depression, preoperative pain, and preoperative patella symptoms have been studied to see their cause-effect relationship on the achievement of forgotten knee status. Published data to date shows no consensus in the relationship between the two. Research is going on to minimize these 20–25% dissatisfied TKA patients all over the world.
As health care costs are ever-increasing worldwide, there has been increasing pressure to economize the TKA procedure by eliminating medical costs that appear not to contribute to the patient’s care. Raab et al.,21 in his article, the cost-effectiveness of routine HP examination stated that “From a societal perspective, there is a trade-off between information gained and the costs incurred from microscopic examinations.” Netzer et al.22 showed that it is unnecessary to perform HP examination on some surgical specimens (e.g., routine tonsillectomies and adenoidectomies) because of these tests’ total cost to the society outweighs the full benefit of the information gained. The main logic of these viewpoints is that the most critical data collected by HP examination should affect individual patient care.21 The same view has been given in various research papers to eliminate HP examination of specimens obtained from hip and knee replacement surgeries. The arguments made in support of this practice are eliminating the HP examination cost benefiting the patient. Generally, there is a lack of disagreement between the clinical and pathological diagnosis, and minor discrepancy in the diagnosis usually does not change the patient management.12, 13, 14, 15, 16, 17 This point of view advocated by these research papers assumes that eliminating the HP examination in no way compromises the quality of care delivered to the individual patient. Greene et al.23 in their study showed that the prevalence of the discrepant diagnosis was 0.7% (twenty seven of 3797); the prevalence of discordant diagnoses was 0.026% (one of 3797). The total cost per discrepant diagnosis was $ 13,771 and the cost per discordant diagnosis was $ 371,810. Their conclusion was the histopathology examination of the tissue removed during knee arthroscopy should be done at the discretion of the orthopedic surgeon rather than being mandatory. Holbrook et al.24 in their study showed that the cost of histologic examination per specimen was $ 48.56. The total cost per discrepant diagnosis was $ 4383. The total cost per discordant diagnosis was $ 122,728. They concluded that the practice of sending the specimen for histopathology during TKA should be decided by the operating surgeon.
As a counterview, pathologists have published articles stressing the importance of routine HP examination.25, 26, 27 The point of view expressed in these research articles is that the HP examination will only detect clinically significant and curable diseases. If missed, the diagnoses of lymphoma or inflammatory arthritis can affect the TKA implant’s survivorship. The majority of the published articles showing the cost-effectiveness of not doing the routine HP examination are more than ten years old with few exceptions.3, 4, 5, 6, 7, 8 Also, all these articles have studied only small numbers of patients. Dicarlo and Klein28 showed that the discordance rate between clinically reported and pathologic diagnoses is much higher than in the previously published literature. A discordant result was defined as a disagreement between the clinically reported and pathologic diagnosis that should not affect patient management. A discrepant result was described as a disagreement between reported clinical and pathologic diagnoses that should be expected to alter patient management. In the hips, the total number of cases for which the clinical diagnosis was verified histologically was 6467 of 7968 cases, for a concordance rate of 81.2% and a discordance rate of 18.8%. In the knees, the total number of cases for which the clinical diagnosis was verified histologically was 7807 of 8619 cases, for a concordance rate of 90.6% and a discordance rate of 9.4%. In the same study, 5.4% of the hips and 1.4% of the knees contained additional discrepant pathologic findings. The discrepant pathologies included PVNS, inflammatory arthritis, granulomas, and malignancy. They concluded that the total savings incurred by eliminating HP examinations are typically less than 0.5% of overall medical costs. They advocated before one elect to save 0.5% of medical expenses by eliminating HP examinations, one must ask oneself if it is worth eliminating 100% of the quality assurance. This study is significant because the patient cohort is much larger, 16,587 patients; two board-certified experienced pathologists carried out the HP examination. Our analysis also shows a concordance rate of 92% and discordance and discrepant diagnoses of 8% and 7%, respectively, which is statistically significant. The patients with the discrepant diagnosis were referred to a Rheumatologist in the postoperative period (at four weeks post-TKR) and were appropriately treated for their inflammatory/rheumatoid arthritis. The FJS-12 score improvement is significant at one-year post TKA compared to preoperative FJS-12 scores in both the concordant and the discrepant diagnoses group. The Improvement in FJS-12 at six weeks in the concordant group (mean 25.3 and SD 17.6) is significantly more than the discrepant group (mean 15.3 and SD 12.5), which is statistically significant, p-value 0.0385. The FJS -12 score comparison at preoperative and at 1-year post TKA interval is not statistically significant (Table 5). We believe this is because the appropriate anti rheumatoid treatment was started at four weeks after the TKA operation and would have taken time to produce results. At a one-year postoperative follow-up, all the patients with discrepant diagnoses are clinically and radiologically doing well. We are following up these patients prospectively to see the impact of this discrepant diagnosis on the clinical performance of the TKA.
5. Conclusion
8% of our patients exhibited unexpected results on the HP examination. This could be one of the many causes in a persistently dissatisfied patient after a technically well-done TKR. Our study clearly showed a 7% rate of discrepant diagnosis, which, if missed, would have affected the function and long-term survival of the implanted TKA. A patient with inflammatory/Rheumatoid arthritis would never have been treated for the same if excised synovium during the TKA surgery was not sent for histological examination. The cost of having almost 7% of dissatisfied TKA patients far outweighs the cost of histological examination incurred by the patient. We conclude that rather than advocating the routine use of histopathology examination of the excised synovium, the operating surgeon should exercise his/her discretion to send the synovium for histopathology examination if he/she finds the synovium to be abnormal. Also, a large multicenter study should be undertaken at various high-volume centers. Such a study would help throw more light on this not so well understood topic and help reduce the percentage of unhappy TKA patients.
Funding
The research did not receive any specific grant from funding agencies in the public, commercial, or not for profit sectors.
Ethics approval
Local ethics committee approval was obtained before the study. Also, all patients consented to participate.
Consent for publication
We hereby give our consent for publication.
Authors’ contributions
All named authors meet the International Committee of Medical Journal Editors (ICMJE) criteria for authorship for this article, take responsibility for the integrity of the work as a whole, and have given their approval for this version to be published.
Availability of data and materials
All data generated or analyzed during this study are included in this published article.
Previous presentation
This data was presented at the International Knee Day of the German Knee Society (DKG) on June 12, 2020 and at the American Association of Hip and Knee Surgeons (AAHKS) meeting at Dallas, Texas 5–8th November 2020.
Declaration of competing interest
The authors declare there are no financial conflicts of interest to disclose.
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Associated Data
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Data Availability Statement
All data generated or analyzed during this study are included in this published article.