|Year : 2022 | Volume
| Issue : 3 | Page : 145-150
Early outcomes of ultra-congruent insert in cruciate-retaining total knee arthroplasty: A prospective study
Sandeep Singh Jaura1, Punit Tiwari1, Harmeet Kaur2, Nitish Bansal3
1 Department of Orthopaedics, Shri Guru Ram Das Institute of Medical Sciences and Research, Amritsar; Department of Orthopaedics, Maharishi Markandeshwar, Medical College and Hospital, Solan, Himachal Pradesh, India
2 Department of Orthopaedics, Shri Guru Ram Das Institute of Medical Sciences and Research, Amritsar; Department of Radiodiagnosis, All India Institute of Medical Sciences, Patiala, Punjab, India
3 Department of Orthopaedics, Shri Guru Ram Das Institute of Medical Sciences and Research, Amritsar; Department of Orthopaedics, Government Medical College, Patiala, Punjab, India
|Date of Submission||18-Feb-2022|
|Date of Decision||01-Mar-2022|
|Date of Acceptance||02-Mar-2022|
|Date of Web Publication||1-Sep-2022|
Department of Orthopaedics, Maharishi Markandeshwar Medical College and Hospital, Kumarhatti, Solan, Himachal Pradesh
Source of Support: None, Conflict of Interest: None
Introduction: The exponents of cruciate-retaining (CR) total knee arthroplasty (TKA) assert that the retention of posterior cruciate ligament (PCL) preserves more normal knee kinematics, femoral rollback on the tibia during flexion, greater stabilization of the prosthesis, and improved position sense as compared to PCL resection TKA. However, one has to shift to the posterior stabilized (PS) femoral component with box and accompanying cam postpolyethylene, especially in cases where PCL is too attenuated to be functional or too tight predisposing to accelerated polyethylene wear. To minimize both the cam mechanism polyethylene wear and the bone sacrifice due to the intercondylar box cut, the ultra-congruent (UC) inserts have been developed that are characterized by a high anterior wall and a deep-dished plate, promising good stability without cam mechanism. Materials and Methods: We did a prospective study to clinically evaluate the short-term results of the patients who underwent TKA using cemented posterior CR implants and UC inserts. PCL was required to be released either partially or completely in all the study patients. Thirty patients were evaluated preoperatively and postoperatively after 12 months with the new Knee Society Knee Scoring System (2011) and the findings were statistically analyzed. Results: There was a statistically significant postoperative improvement in flexion (from mean of 87.69° to 111.53°, P = 0.000), objective knee indicators (33.53 ± 8.51–70.84 ± 4.91, P = 0.000), patient satisfaction scores (7.48 ± 2.12–21.53 ± 4.26, P = 0.000), and the functional activities score (32.53 ± 5.12–69.02 ± 6.36, P = 0.000). We did not note any disadvantage of CR TKA with UC insert and no patient underwent an early revision for instability. Conclusion: Using UC insert in CR TKA is a reliable procedure that has decreased the dependence on the PS designs.
Keywords: Arthroplasty, knee, polyethylene, replacement, ultra congruent
|How to cite this article:|
Jaura SS, Tiwari P, Kaur H, Bansal N. Early outcomes of ultra-congruent insert in cruciate-retaining total knee arthroplasty: A prospective study. J Orthop Dis Traumatol 2022;5:145-50
|How to cite this URL:|
Jaura SS, Tiwari P, Kaur H, Bansal N. Early outcomes of ultra-congruent insert in cruciate-retaining total knee arthroplasty: A prospective study. J Orthop Dis Traumatol [serial online] 2022 [cited 2023 Jun 6];5:145-50. Available from: https://jodt.org/text.asp?2022/5/3/145/355236
| Introduction|| |
The exponents of cruciate-retaining (CR) total knee arthroplasty (TKA) assert that the posterior cruciate ligament (PCL) has proprioceptive function and is the primary restraint to the posterior translation of the tibia throughout the full range of knee flexion, its retention preserves more normal knee kinematics, femoral rollback on the tibia during flexion, greater stabilization of the prosthesis, and improved position sense as compared to PCL resection TKA.,,,,,
Furthermore, the PCL – retaining designs do not require much alteration in the level of the joint line while balancing the flexion and extension gaps, as compared to the PCL substituting counterparts which frequently balance with mild elevation of the joint line which may alter patellofemoral mechanics and result in postoperative pain and subluxation.
However, preserving PCL and using CR femoral component is not always possible, especially in cases where PCL is too attenuated to be functional or too tight predisposing to accelerated polyethylene wear. In this situation, one has to shift to posterior stabilized (PS) femoral component with box and accompanying cam postpolyethylene insert. Using PS design, we can avoid the postoperative rupture of PCL either due to trauma, inflammatory disease process, or degeneration over time which may lead to late instability. This complication can also occur iatrogenically while performing CR TKA when the PCL is overzealously recessed for balancing or excessive proximal tibial resection is performed which may compromise the PCL insertion site. The PS TKA implants avoid the above-discussed problems but have a high risk of cam-mechanism polyethylene wear.
To minimize both the polyethylene wear and the bone sacrifice due to the intercondylar box cut, new types of inserts have been developed to increase the implant conformity and to reduce stresses on the bone–implant interface. The ultra-congruent (UC) inserts hence developed, are characterized by a high anterior wall and a deep-dished plate, promise good stability without cam mechanism.
These highly conforming inserts with anterior build-up act as an alternative to the cam post-PS TKA design using deep-dish design which gives full stability and the elevation of the polyethylene insert's anterior rim prevents the anterior displacements of the femoral condyles on the tibia with knee flexion. It eliminates the need for resection of the intercondylar notch bone stock and the use of a tibial post which also avoids the patellar clunk syndrome.
The UC insert has, at least theoretically, the advantage of evenly distributing the loads over a larger surface area of the polyethylene insert and ultimately at the bone–implant interface.
This study evaluated the early clinical and functional outcomes of CR knee with UC insert.
| Materials and Methods|| |
After taking approval from the institutional ethical committee of our institute, which is a medical college teaching institute, we did a prospective study on the outcome of patients who underwent TKA using cemented posterior CR implants and UC inserts from July 2015 to June 2017.
The study aimed to clinically evaluate the short-term results of TKA with UC insert with CR TKA design. The objective was to compare the preoperative and postoperative knee scores at 1-year follow-up using the new Knee Society Knee Scoring System (2011).
Thirty-two patients were enrolled in this study, of which two cases were lost to follow-up. Informed consent was obtained from all the participants and they were followed up for 12 months.
The collection of data from patients, who underwent TKA are as follows:
- History by verbal communication
- Clinical examination
- Preoperative and postoperative data evaluation using new Knee Society Knee Score (2011).
- Osteoarthritis Grade III and IV (Kellgren-Lawrence Classification 1957)
- Age >55 years with no clinical or radiological evidence of inflammatory arthropathy.
- Revision TKA
- Inflammatory arthritis
- History of significant trauma in the past
- Age <55 years
- Valgus deformed knees.
All the surgeries were performed by a single surgeon under combined spinal and epidural anesthesia. An Intravenous antibiotic cefuroxime 1.5 g was given 45 min before tourniquet inflation. A standard midline approach with the knee in flexion was used from the upper pole of the patella to tibial tuberosity. A minimal medial and posteromedial release was done as per preoperative varus deformity. Tibial and femoral osteophytes were excised. Tibial and femoral resections were made as per the preoperative plan and implant specifications. Flexion-extension gap was balanced. PCL was required to be released either partially or completely in all the study patients depending on the intraoperative findings. The patella was not resurfaced in any of the participants and only osteophyte removal was deemed sufficient. We used cemented posterior CR implants and a UC inserts in all cases. Tourniquet was released, hemostasis was achieved by cauterization. A drain was placed and the wound closed in layers.
We employed the following postoperative protocol for patients.
Intravenous antibiotics were administered postoperatively for 3 days. Postoperative pain was controlled by patient-controlled epidural elastomeric pump. Deep vein thrombosis (DVT) prophylaxis was initiated after 6 h of surgery. The drain was removed on next day and static quadriceps strengthening exercises and active straight leg raising were started as permitted by the pain.
On the 2nd day, active-and passive-assisted flexion and extension were started, as tolerated by the patient. Moreover, assisted ambulation was encouraged with the help of a walker.
Active exercises were encouraged including flexion and extension, assisted walking. By the time the sutures were removed (12–14 days), patients were encouraged to have the good muscle strength and knee control. The majority of patients could walk without aid after 2 weeks of surgery. DVT prophylaxis was administered for 7 days and followed by oral tablet aspirin 75 mg once a day (OD) for the subsequent 3 months.
Patients were evaluated preoperatively and postoperatively after 12 months with the new Knee Society Knee Scoring System (2011). The new Knee Society Knee Scoring System is both physician and patient-derived. It includes versions to be administered preoperatively and postoperatively. It has an initial assessment of demographic details, including an expanded Charnley functional classification. The objective knee score, completed by the surgeon, includes a Visual Analog Scale score of pain walking on level ground and stairs or inclines, as well as an assessment of alignment, ligament stability, and ROM, along with deductions for flexion contracture or extensor lag. Patients then record their satisfaction, functional activities, and expectations.
The 2011 Knee Society Score consists of four separate components: objective, satisfaction, expectation, and functional score:
(1) An “Objective” knee score (seven items: 100 points), (2) A Patient Satisfaction Score (five items: 40 points), (3) A Patient Expectation Score (three items: 15 points), and (4) A Functional Activity Score (19 items: 100 points). Hence, it should be reported as four separate scores one for each component. These components are separate parameters and so cannot be totaled to make a single score with statistical validity.
The findings of this study were statistically analyzed with Statistical Package For The Social Sciences (IBM Corp. Released 2019. IBM SPSS Statistics for Windows, Version 26.0. Armonk, New York) for functional scores, ranges of motion, radiographic outcomes, and complications.
| Results|| |
In this study, 32 patients were enrolled who underwent CR TKA with UC insert. All the patients were followed up for 12 months. Two patients were lost to follow-up.
The mean age of the patients was 63.1 ± 5.30 years with other demographic details summarized in [Table 1]. The mean of preoperative flexion was 87.69° which significantly improved to a mean of 111.53° postoperatively (P = 0.000) following CR TKA. The range of motion-wise distribution of patients is given in [Table 2].
[Table 3] demonstrates the pre-and postoperative fixed flexion deformity. [Table 4] shows the mean ± standard deviation and P of preoperative and postoperative scores of the 2011 Knee Society Score. There was a statistically significant postoperative improvement in flexion (from mean of 87.69° to 111.53°, P = 0.000), objective knee indicators (33.53 ± 8.51–70.84 ± 4.91, P = 0.000), patient satisfaction scores (7.48 ± 2.12–21.53 ± 4.26, P = 0.000), and the functional activities score (32.53 ± 5.12–69.02 ± 6.36, P = 0.000). However, the postoperative expectation score was not improved significantly. [Figure 1] illustrates the pre-and postoperative objective knee indicator score. The postoperative objective indicator score (blue line) shows progressive improvement after CR TKA design with UC insert. The patient expectation score of the 2011 KSS is shown in [Figure 2]. The postoperative patient expectation score blue line was not significantly improved than the preoperative score (red line). In the present study, patient expectation scores may appear to worsen postoperatively, due to a difference in the contents of questionnaires used preoperatively and postoperatively. The preoperative version includes the expectations of postoperative outcomes, whereas the postoperative version refers to superiority or inferiority between the knee condition expected preoperatively and postoperatively. Furthermore, the patient–surgeon relationship, including the content of informed consent, may influence the expectation score more than other categories. An inadequate clarification of the operation, including the surgical procedure, possible complications, and postoperative rehabilitation, can lead to disappointing results for the patients.
|Figure 1: Comparison of preoperative and postoperative objective knee indicator score|
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In [Figure 3] of preoperative and postoperative functional score, the X-axis is the number of total knees (39) and the y-axis is the functional score which contains maximum of 100 points. In preoperative graph plot (red line) indicates that all 39 knees fall in between 25 (minimum) and 57 (maximum) points which are the very poor functional score but after TKA with UC insert this functional score improved to 54 (minimum)–83 (maximum) which is significant.
[Figure 4] is a comparison of preoperative and postoperative symptoms (pain). It shows a significant reduction of pain in postoperative patients. The present study found that the postoperative range of motion positively correlated (r = 0.355; P = 0.026) with preoperative satisfaction [Figure 5] and [Table 5].
|Figure 5: Scatter diagram of the relationship between preoperative satisfaction and postoperative range of motion of the knee|
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|Table 5: Relationship between preoperative satisfaction and postoperative range of motion of the knee|
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| Discussion|| |
Plenty of research articles comparing the PS and CR knee design are freely available in the literature. However, there is a paucity of research articles that have evaluated the outcomes of CR design with the UC component.
Rajgopal et al. conducted a study aimed to investigate any differences in functional outcomes between two different polyethylene designs, namely the Persona CR and Persona UC tibial inserts. In this prospective single-blind, single-surgeon randomized controlled trial, 105 patients were assessed in terms of function and gait. The modified Knee Society Scores and knee range of motion (ROM), evaluated preoperatively and postoperatively at 6 months, 1 year, and 2 years showed better outcomes in terms of statistics (P < 0.05) for UC inserts.
Song et al. recruited patients who had been treated with CR or UC TKAs (38 cases in each group), after a minimum 3-year follow-up and hypothesized that patients with the UC insert would not show significantly different in vivo stability or functional outcomes from those in the CR group. The same surgical technique was used in both groups with the same femoral components, except for the polyethylene inserts (CR or UC). Both the CR and UC groups showed significant improvements in postoperative ROM, HSS, KS, and WOMAC scores without intergroup differences between the two groups. Moreover, there were no differences in mediolateral or anteroposterior laxity between the two groups (P > 0.05).
In their randomized controlled study, Akti et al. also concluded that the use of UC or PS inserts in TKA did not affect the clinical outcomes or isokinetic performance, hence, the potential differences in performance between UC and PS inserts need not be considered when sacrificing the PCL in TKA.
Similar results have been demonstrated by Shi and Tian who concluded in their study that there is no obvious difference between PS and UC in TKA and UC insert seems to be a practical alternative to the PS.
A study, exclusively evaluating different CR bearing insert designs, was published by Berend et al. in which they compared a standard CR tibial insert with 3° posterior slope and no posterior lip (CR-S) and an insert with no slope and a small posterior lip (CR-L) and a deep-dish, anterior stabilized insert (CR-AS). The mean improvement in ROM was highest for the CR-AS inserts 5.9° (−40°–55°) versus CR-S 3.1° (−45°–70°) versus CR-L 3.0° (−45°–65°); (P = 0.004). There was a significantly higher manipulation under anesthesia (MUA) rate with the CR-S and CR-L inserts than CR-AS (Pearson rank 6.51; P = 0.04). The CR-AS design recorded no failures for instability and provided more improvement in ROM than other designs and was associated with less stiffness requiring MUA.
Scott and Thornhill reported on 100 primary CR-TKRs, comparing 50 with flat posterior lipped tibial inserts with 50 with curved inserts. They observed no differences in ROM or incidence of tibial radiolucencies between the groups and noted that the conforming bearings provide a tempting combination of the designs for cruciate preservation and cruciate substitution.
Hofmann et al. conducted a study of two matched groups of 100 TKRs in which they compared very congruent inserts with CR inserts. At the mean 5-year follow-up, hospital for special surgery and ROM scores were similar between both groups. However, five TKRs with PCL-sparing inserts had been revised for AP instability and PCL insufficiency, compared with none in the very congruent group.
In our study, involving UC insert with CR Knee, the average preoperative functional knee score was 32.53. The postoperative average functional score was 69.02, which is a good improvement with a significant P = 0.000, indicating a significant improvement.
The preoperative satisfaction score (A subcomponent of 2011 KSS) positively correlates with the postoperative range of motion, i.e., the patients who have higher satisfaction scores preoperatively may acquire more successful outcomes of the ROM. This finding indicates that the surgeon may predict the patient-derived outcome of ROM through comprehending the patient's preoperative satisfaction.
The most significant finding was that all the patient-derived scores except for patient expectation significantly improved postoperatively. The mean preoperative expectation was 9.48 and the mean postoperative score was 9.71 with the mean difference of 0.23 with P = 0.173 which is indicated nonsignificant improvement.
Throughout our study, we did not note any disadvantage of CR TKA with UC insert. Neither any patient had an acute complication such as hematoma, infection, or neurovascular compromise, nor did anyone undergo an early revision for instability or loosening.
However, our study has a limitation of small sample size, lack of comparison group, and short follow-up of only 1 year which yielded only early observations. Multicentric studies with larger study cohorts with comparison groups and mid-term to long-term follow-up will better help make a clear verdict.
One may feel that Stefl and Meneghini, in their 2019 article, have gone overboard to label the PS designs as vestigial organs in modern TKA. However, we would like to go with Lützner et al. that it can be safely said that the UC insert can decrease the dependence on the PS designs and helps us reap the benefits of the CR femoral component even in the absence of PCL and provides pain relief, adequate stability, and an excellent improvement in ROM with good function.
| Conclusion|| |
UC insert in CR TKA is a reliable procedure that could provide good short-term results in our study.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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