Abstract
Background
Total Knee Arthroplasty (TKA) is the gold standard of treatment for end stage arthritis not responding to conservative treatment. With a recent increase in the younger population presenting with osteoarthritis (OA) we undertook this study to evaluate long-term outcomes and survivorship of TKA in this cohort.
Materials and Methods
Our study cohort included 328 patients, < 55 years, with OA, who underwent TKA using Cruciate Retaining (CR), and Posterior Stabilized (PS) implants with a minimum follow up of 15 years. Revision surgery was the end point of our analysis and Kaplan–Meier evaluation of survivorship was measured. Knee Society Scores (KSS) and Range of Motion (ROM) were assessed to evaluate outcomes.
Results
Survivorship of the CR and PS implants with revision as end point, for aseptic loosening was 97.3% and 96%, and revision for all causes was 89.7% and 86.1%, respectively, at 15 years. The outcomes of CR implants were better than the PS cohort in terms of function and survivorship.
Conclusion
Long term survivorship and outcome analysis of TKA in patients < 55 years showed good results with excellent survivorship, with both CR and PS implants. The CR cohort demonstrated better long-term survivorship, though the difference was not statistically significant. Deep infection and aseptic loosening were the commonest causes for failure.
Keywords: Total knee arthroplasty (TKA), Cruciate retaining (CR), Posterior stabilized (PS), Survivorship
Introduction
Total knee arthroplasty (TKA) is an established treatment option for end stage arthritis. Data from the Swedish [1], and Australian registry [2] and the CDC (Centers for Disease Control and Prevention) [3] shows an increase in the numbers of TKAs done for arthritis in the younger population [4]. Data from the Medicare population showed a 161.5%increase in the percentage of young patients undergoing TKA from 1991 to 2010 [5]. With an estimated 27 million cases of clinical OA reported in adults [6] and the demand for primary TKA projected to increase by 673% by the year 2030 [7] it becomes imperative to understand the outcomes of TKA in the younger population.
The advancement in quality of implant designs and refinement of surgical techniques for TKA has led to significant improvement in the survival of TKA. However, younger patients with higher activity levels [8] and greater expectations pose a challenge to prosthesis survivorship.
Current available literature reviews of TKA in the young population consists of short to mid-term follow-up [9–12]. Kim et al. however reported encouraging results of fixed and rotating platform knees [13] at a long term follow-up. The Australian joint registry reports higher rates of revision in patients under age 55 years compared to older age cohorts [2]. The revision rates at 10, and 15 years following TKA in the under 55 cohorts has been reported to be 10.9 and15.7% respectively [14]. Other authors, using conventional scoring systems have reported significant improvement in clinical and functional scores following TKA in young patients, with implant survival rates of 90–99% in the first postoperative decade and 85–96% in the second [15]. We present a comprehensive analysis of the outcome and long-term survivorship of TKA in young OA patients aged less than 55 years. The aim of our study was to evaluate the outcomes and survival rates of TKA (both cruciate retaining and posterior stabilized) in this cohort of patients.
Materials and Methods
This study included a group of 360 patients under the age of 55 years, who underwent TKA for degenerative arthritis, operated between December 1997 and December 2003. All patients were evaluated preoperatively for ROM, disability, KSS and the need for walking aids. Radiological evaluation included full-length weight bearing radiographs to assess limb alignment and deformity. The knees were categorized on the basis of severity of arthritis by Kellgren Lawrence grading system and operated by a single senior surgeon. The study was conducted after approval from the institutional board ethics committee. Of the 360 patients recruited for the study, 18 refused participation, 12 were lost to follow-up (untraceable) and 2 died during the course of the study. A total of 328 patients (117 males, 211 females; 328 knees) were followed till December 2018. Of these 328 knees, 184 had grade 3 and 144 had grade 4 arthritic changes as categorized by Kellgren Lawrence grading system. Inclusion criteria were patients under the age of 55 years, with degenerative arthritis, who had no prior surgical intervention. Cases with extra-articular deformity and post traumatic arthritis were excluded. Preoperatively, 36% of the patients needed a walking aid for ambulation. The average Charlson Comorbidity Index score was 2 in this cohort. The mean age of patients in this study was 51.5 ± 3.7 years.
Cruciate retaining implants were used in 204 and posterior stabilized in 124 patients. The minimum period of follow up for all patients in this study was 15 years (range 15 to 21). The mean BMI was 26.4 ± 2.5 in the CR group and 26.0 in the PS group (Table 1).
Table 1.
Baseline characteristics of both the groups
| Parameters | OA group | |||
|---|---|---|---|---|
| CR (N = 204) |
PS (N = 124) |
Total (n = 328) |
P value | |
| Age (years) (mean ± SD) | 51.2 ± 3.6 (44–55) | 52.0 ± 3.7 (43–55) | 51.5 ± 3.7 (43–55) | 0.067 |
| BMI (mean ± SD) | 26.4 ± 2.5 (22.2–31.6) | 26.0 (23.5–31.6) | 26.2 ± 2.5 (22.2—31.6) | 0.216 |
| Gender, n (%) | ||||
| Male | 80 (68.0%) | 37 (32.0%) | 117 (100.0%) | 0.179 |
| Female | 120 (57.0%) | 91 (43.0%) | 211 (100.0%) | |
Implant selection bias was minimized using a single manufacturer (Nexgen CR, Legacy PS, Zimmer, Warsaw, Indiana, USA) which included CR and PS implants. All patients were operated under tourniquet control (mean pressure of 270 mmHg) using a medial parapatellar approach. Appropriate soft tissue releases were done to obtain good correction and a balanced knee. No pie crusting of the Medial Collateral Ligament (MCL) or medial or lateral epicondylar osteotomy was done in any patient in this study. All patients received a periarticular analgesic cocktail in the posterior capsule (40 ml of 0.25%Bupivacaine + 0.5 ml Clonidine + 0.5 ml Adrenaline). The patella was not resurfaced in any of the patients, but excellent extensor mechanism tracking was ensured using the no thumb technique. All the implants were cemented using first generation digital pressurization technique after thorough lavage. All patients received three doses of intravenous second generation cephalosporins, first dose at the time of induction, second after 12 h and third 24 h after surgery. Similar post-operative rehabilitation protocol was followed for all the patients including DVT prophylaxis in the form of cryotherapy, pressure garments, DVT pump and early mobilization. All patients were administered Inj Clexane 60 mg subcutaneously during hospitalization and discharged on oral Aspirin 75 mg once daily for a period of 3 weeks. The clinical and radiological evaluations of the patients were done immediate postoperatively, at three months, twelve months and every 2 years thereafter by the senior surgeon and an experienced physiotherapist. Immediate postoperative radiological evaluation was done to evaluate the posterior tibial slope and coronal plane alignment. ROM assessment and KSS were evaluated at each visit.
The surgical goal was to achieve an overall alignment of 5° valgus relative to the mechanical axis of the femur in varus knees and 3° in valgus knees. The tibial resection was done at 90° to the mechanical axis of the tibia replicating the native posterior tibial slope. Radiological evaluation was done using weight bearing antero-posterior, lateral and skyline views. The radiographs were evaluated at each follow up for any evidence of radiolucent lines and their progression to indicate loosening. Any alteration in the position of the implants was also noted.
Statistical Analysis
The analysis included profiling of patients on different demographic and clinical findings. Quantitative data were presented in terms of means and standard deviation or median with inter-quartile range (IQR). Qualitative/categorical data were presented as absolute numbers and proportions. Cross tables were generated and chi square test was used for testing of association between categorical variables. For quantitative variable, Independent Student t test was used for testing of mean difference between two independent groups whereas Paired Student t-test was used for pre–post analysis. The primary outcome was measured as prosthesis survival time, defined as the proportion of prostheses surviving without revision (any surgery which needed replacement of components including the tibial insert exchange) during the follow up period. Prosthesis survival was calculated using the Kaplan–Meier-Method and compared using a two-sided log rank test. Life table analysis was used to determine the prostheses survival rate at 5, 10, 15 years and at last follow-up with an end point of revision in both the groups. P-value < 0.05 was considered statistically significant. SPSS software Version 24.0 was used for statistical analysis.
Results
Knee Society Scores
The knee society clinical score (KSCS) of patients improved from preoperative values of 46.0 ± 4.1 and 45.4 ± 3.4 to 82.8 ± 4.9 and 82.0 ± 4.0 postoperatively in the CR and PS cohorts respectively (P-value CR vs PS 0.146) at final follow up.
The knee society functional score (KSFS) improved from 44.9 ± 3.7 and 44.1 ± 4.5 preoperatively to 84.2 ± 5.1 and 83.3 ± 5.5 post operatively in the CR and PS groups (P-value CR vs PS is 0.151). The postoperative mean posterior tibial slope was 4.9 ± 2.1°. The femoral valgus cut was measured to be 3.4 ± 1.8° from the mechanical axis of the femur. Non progressive radiolucent lines were seen in 14 PS and 10 CR knees at the time of final follow up.
Range of Motion
The mean range of motion (ROM) in CR and PS group improved from mean 99.4 ± 3.3° and 98.9 ± 3.0° preoperatively to 125.7 ± 3.8° and 125.1 ± 3.1° post-operatively respectively (P = 0.070 CR vs PS) at last follow up (Table 2).
Table 2.
Clinical outcomes (KSCS, KSFS and ROM)
| OA | P value | ||
|---|---|---|---|
| CR | PS | ||
| Knee society clinical score (points)(KSCS) | |||
| Preoperative | 46.0 ± 4.1 | 45.4 ± 3.4 | 0.125 |
| At last follow-up | 82.8 ± 4.9 | 82.0 ± 4.0 | 0.146 |
| P value | < 0.0001 | < 0.0001 | – |
| Knee society functional score (points) (KSFS) | |||
| Preoperative | 44.9 ± 3.7 | 44.1 ± 4.5 | 0.097 |
| At last follow-up | 84.2 ± 5.1 | 83.3 ± 5.5 | 0.151 |
| P value | < 0.0001 | < 0.0001 | – |
| Range of motion (degrees) (ROM) | |||
| Preoperative | 99.4 ± 3.3° | 98.9 ± 3.0° | 0.155 |
| At last follow-up | 125.7 ± 3.8° | 125.1 ± 3.1° | 0.070 |
| P value | < 0.0001 | < 0.0001 | – |
Revision Surgery
A total of 31 knees were revised (9.4%). The two most common reasons for failure were infection (5 CR and 3 PS) and aseptic loosening (4 each in CR and PS knees). The other indications for revision included 4 cases of peri-prosthetic fractures, 3 case of late instability, 5 case of polywear, and 3 case of quadriceps tendon rupture (Table 3).
Table 3.
Indications for revision
| Indications | CR | PS | Total 14 |
|---|---|---|---|
| 17 | 14 | 14 | |
| Infection | 5 | 3 | 8 |
| Aseptic loosening | 4 | 4 | 8 |
| Poly-wear | 2 | 3 | 5 |
| Instability | 2 | 1 | 3 |
| Peri-prosthetic fracture | 2 | 2 | 4 |
| Rupture of quadriceps tendon | 2 | 1 | 3 |
| Malrotation | 0 | 0 |
17 CR TKAs (8.3%) and 14 PS (10.5%) TKAs were revised. Of the cases revised for aseptic loosening optimal alignment was achieved in 5 knees post-operatively, while 3 knees had a post-operative varus malalignment of 5°–7°. All deep infections (5CR and 3 PS) were managed by a two-stage exchange arthroplasty and other failure modes (aseptic loosening 8, instability 3, rupture of quads tendon 3, polywear 5,) were treated by revision procedures using stem extensions and constrained options (PS in 8, LCCK in 11 knees). Peri-prosthetic fractures (4) were treated by open reduction and internal fixation in 2, and revision knee arthroplasty using a rotating hinge and tantalum cones in the other two patients.
Kaplan–Meier Survivorship Analysis
The Kaplan–Meier estimate for survival when end point selected was revision for any cause was 96.1%, 93% and 89.7% for the CR and 96.8%, 91.7% and 86.1% for the PS cohort at 5, 10 and 15 years respectively. When aseptic loosening as reason for failure was considered as the end point, the survival rates of CR implants were 99%, 98.5% and 97.3% at 5, 10 and 15 years respectively and 98.4%, 97.5% and 96% at 5, 10 and 15 years for the PS implants respectively (Table 4, Figs. 1, 2).
Table 4.
Survival rate analysis in total knee arthroplasty
| Knee | Survival rate (95% CI) | ||
|---|---|---|---|
| 5 years | 10 years | 15 years | |
| Revision due to any causes | |||
| PS | 96.8% (93.7–99.9%) | 91.7% (86.8–96.6%) | 86.1% (80–92.2%) |
| CR | 96.1% (93.4–98.8%) | 93% (89.5–96.5%) | 89.7% (85.5–93.9%) |
| Total | 96.3% (94.3–98.3%) | 92.5% (89.6–95.4%) | 88.2% (84.7–91.7%) |
| Aseptic reasons for failure | |||
| PS | 98.4% (96.2–100.0%) | 97.5% (94.8–100.0%) | 96% (92.6–99.4%) |
| CR | 99% (97.6–100.0%) | 98.5% (96.8–100.0%) | 97.3% (95.1–99.5%) |
| Total | 98.8% (97.6–100.0%) | 98.1% (96.6–99.6%) | 96.8% (94.9–98.7%) |
Fig. 1.
Kaplan–Meier curve for revision due to any causes
Fig. 2.
Kaplan–Meier curve for revision due to aseptic loosening
Discussion
The success of TKR is well documented in terms of pain relief and implant survivorship [16, 17] but many surgeons arbitrarily reserve TKA for patients older than 60 years in view of the reported poorer outcomes associated when the procedure is performed in the younger population [18, 19]. Paxton et al. [20] noted a relatively higher risk of 2.56% signifying a two-fold increased risk of revision TKA in the younger age group in comparison to patients in the older cohort. The Australian registry reported four issues which impacted the revision rate- minimally stabilized prosthesis, patellar resurfacing, highly cross-linked polyethylene, and use of computer navigation were associated with lower revision rates [14]. The yearly cumulative revision rate at 10 years for TKA patients less than 55 years of age was 12.1% as per the annual report of Australian Orthopaedic Association National Joint Registry [2]. Wood et al. [21] evaluated and compared outcomes and knee performance of two cohorts of patients, < 55 years and > 55 years of age, who underwent TKA. They noted similar outcomes and concluded that the younger age group should not be considered a barrier for TKA. Crowder et al. [4] noted a near 100% survival rate for TKAs in the younger population aged 55 or less at 5 and 15 years respectively. We evaluated the survivorship and functional scores of patients with OA who were treated by CR and PS implants to check if either implant scored differently. Our results compare favorably with those reported in literature [9, 10, 18, 23, 24]. Lonner et al. [9] reported a 90.6% survivorship at 8 years in a cohort with a mean age of 35 (n = 32) in an osteoarthritic population with both CR and PS implants showing comparable results. Abdel et al. [24] compared the survival rates of CR and PS at 15 years and reported significantly improved survival with the CR prosthesis as compared to the PS option. The age group of patients in the study was however not specified. Odland et al. [25] reported a survival rate of 93% at 10 years and 81% at 18 years in a cohort of 67 patients regardless of the type of implants used.
Kim et al. [13] compared the survivorship of fixed bearing and rotating platform prostheses in the young population and reported a 95% survival rate for fixed bearing CR prostheses and 97% for rotating platform PS prostheses in 108 patients aged less than 51 years with OA at mean follow up of 16.8 years. Parvizi et al. [26] reported on almost 33% patients with residual symptoms, although the pain relief was 91%.
In our study CR implants had a survival rate of 89.7% and PS implants had a survival rate of 86.1% at 15 years when end point was revision for any cause. The survival rates for aseptic causes were 97.3% (95% CI, 95.15–99.5%) and 96% (95% CI, 92.6–99.4%) for CR and PS implants respectively. Crowder et al. [4] documented a 100% survival rate using mixed implant designs at 15 years and 93.7% at 20 years for 32 TKA in OA patients under 55 years of age. Meding et al. [27] reported a survival rate of 96.5% at 15 years in his series of 212 patients with arthritis treated by PS implants.
Lonner et al. [9] reported 4 revisions for aseptic loosening in 32 TKAs at a follow up of 7.9 years. Dalury et al. [11] at an average follow up of 7.2 years reported 2 revisions for patellar component failure and 1 for infection in 103 cemented TKAs in patients younger than 45 years.
We had a total of 31 TKAs requiring revisions (9.5%). Of these 17 were in the CR (8.3%) and 14 in the PS cohort (10.4%). There were 8 revisions for aseptic loosening, 8 for deep infections, 4 for periprosthetic fractures, 3 for instability, 5 for poly-wear and 3 for rupture of quadriceps tendon.
Long-term survivorship of implants is dependent on achieving optimal alignment, good soft tissue balance, and good fixation. Malalignment has been described as one of the causative factors in early loosening [28]. Younger patients with higher activity levels demand excellent soft tissue balance and optimal alignment to achieve good long term outcomes and survivorship [22–24].
Both CR and PS TKAs demonstrated significant improvement in the KSS. The post-operative ROM was similarly found to be significantly improved in both CR and PS groups (Table 2).
Our study also observed that the prosthesis survival rate with CR knees was better than the PS knees at final follow up. This result corroborates well with other studies reporting good outcomes using CR implants in terms of function and survivorship in OA [17, 29]. Many authors have reported on relatively small sample sizes [9, 10, 14, 18, 30] while other authors have used both cemented and uncemented fixation options [9, 30]. Most of these series included patients with patellar resurfacing [9–11, 18, 24, 30].
Limitations
Our study has its limitations—one being that the design was retrospective in nature. About 12 patients were untraceable during the course of the study and 18 refused participation though at the last follow-up, as per hospital records, the implants were functioning well. Another limitation of this study was the fact that a few of the patient were evaluated by telephonic consultations, due to inaccessibility.
Conclusion
The results of our study indicate excellent long-term survivorship of cemented TKA in young patients with osteoarthritis using both CR and PS implants. The CR cohort demonstrated better long-term outcomes and survivorship, though this difference was not statistically significant. The main causes of failure in this study were aseptic loosening and infection. Polyethylene wear also contributed significantly to the failure mode. Attention to detail, correct soft tissue balancing and achieving correct rotational alignment are critical for long-term survivorship and good clinical outcomes.
Acknowledgements
We acknowledge the contribution of Mr Manish Kumar in helping with the statistical analysis and calculations.
Author contribution
All authors contributed towards the preparation of the manuscript, evaluating outcomes and results.
Funding
There were no financial or material support taken in this study.
Declarations
Conflict of interest
The authors declare that they have no competing interests.
Ethical approval
Ethical committee clearance was taken for this study by Medanta Institutional Review board.
Informed consent and publication consent
Informed consent and publication consent was taken from all subjects included in the study. approval.
Contributor Information
Ashok Rajgopal, Email: a_rajgopal@hotmail.com.
Sumit Kumar, Email: sumit_kumar_83@yahoo.com.
Kalpana Aggarwal, Email: kalpanaa@live.com.
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