Minimum 5-year Follow-up Results of Minimally Invasive Total Knee Arthroplasty Using Mini-Keel Modular Tibial Implant

Outcomes of total knee replacement with the use of a NexGen MIS Tibial Component (Mini-keel) : a systematic review

NexGen MIS Tibial Component (Mini-keel) is a tibial component specially developed for minimally invasive surgery in total knee replacement (TKR), and the size limitations of its design and the modular system could affect tibial fixation strength, however, this has not been precisely evaluated thus far. This study aimed to systematically review the literature describing the outcome following TKR with the use of a Mini-keel. Electronic searches of databases were undertaken in July 2019 by two experienced orthopaedic surgeons according to the PRISMA guidelines for literature describing the outcomes of TKR with the use of a Mini-keel. Quality of studies was assessed using the Joanna Briggs Institute Critical Appraisal Checklist. The initial search found a total of 623 studies from all the databases. Seven studies met all the inclusion criteria and were eligible for critical appraisal and quality assessment. In total, 2,198 cases were included in the systematic review. Thirty-five revision cases due to aseptic loosening were found from the systematic review. Two studies were negative about using a Mini-keel and three studies were positive about it, while the other two studies did not judge the quality of a Mini-keel. There have been conflicting conclusions among studies for the use of a Mini-keel. There remains a paucity of prospective cohort studies between TKRs with the use of a Mini-keel and those with the use of a conventional implant, which makes it difficult to determine the usefulness and reliability of this implant.

Minimally invasive surgery total knee arthroplasty is less popular, but the prosthesis designed specifically for MIS provides good survival and PROMs with a minimum follow-up of 10 years

BACKGROUND

The concept of minimally invasive surgery (MIS) was introduced in total knee arthroplasty (TKA) in the late 1990s. The number of MIS TKAs has clearly decreased in recent years. An implant designed specifically for MIS TKA has been used all over the world, but there are no reports of long-term postoperative results. The purpose of this study was to characterize long-term clinical results with a minimum follow-up of 10 years.

METHODS

This retrospective study included 109 consecutive patients with 143 NexGen CR-Flex prostheses, which are MIS tibial component prostheses designed specifically for MIS TKA. Twelve-year survival analysis was performed using Kaplan-Meier method. Revision surgery for any reason was the endpoint. Long-term clinical and radiographic results of 74 knees (55%) in 60 patients with more than 10 years of follow-up were analyzed.

RESULTS

The cumulative survival rate of the single-radius posterior-stabilized TKA of 74 knees was 94.7% (95% confidence interval, 90-99%) at 12 years after surgery. Seven knees (9%) required additional surgery during the 10-year follow-up because of periprosthetic infections. Mean postoperative Knee Society knee score and functional score were 91 and 74 points, respectively. There were no cases of prosthesis breakage, polyethylene wear, or aseptic loosening of the prosthesis.

CONCLUSION

The prosthesis designed specifically for MIS TKA is associated with good survival and clinical results with a minimum follow-up of 10 years, even though MIS TKA has become less popular.

LEVEL OF EVIDENCE

III.

Does Obesity Affect Clinical and Radiological Outcomes in Minimally Invasive Total Knee Arthroplasty? Minimum 5-Year Follow-up of Minimally Invasive TKA in Obese Patients

Background

The aim of this study was to evaluate the clinical and radiological outcomes of minimally invasive total knee arthroplasty (MIS-TKA) in obese patients.

Methods

We examined the records of 371 cases of MIS-TKA performed using the mini-midvastus approach from January 2006 to December 2006. According to body mass index (BMI), the cases were classified into group A (BMI < 25 kg/m², 114 knees), group B (25 kg/m² ≤ BMI < 30 kg/m², 179 knees), and group C (BMI ≥ 30 kg/m², 78 knees). Clinical outcomes were measured with the Hospital for Special Surgery Score and Knee Society Score. Radiological evaluation included measurements of knee alignment.

Results

MIS-TKA was performed on all patients. The skin incision size in group A, group B, and group C was 8.2 ± 0.8 cm, 8.3 ± 0.8 cm, and 8.5 ± 0.9 cm, respectively, and the operation time was 86.4 ± 10.4 minutes, 85.9 ± 11.3 minutes, and 89.0 ± 11.4 minutes, respectively, indicating no significant difference among the groups (p > 0.05). There was no difference in terms of the accuracy of the tibial implant alignment, with 97.6%, 95.2%, and 93.4% of each group showing 90° ± 3° varus angulation (p > 0.05). With respect to the accuracy of the femorotibial angle, 93.9%, 94.6%, and 90.2% of each group had 6° ± 3° valgus angulation, with group C demonstrating the lowest level of accuracy (p < 0.05). The preoperative range of motion and Knee Society Score of group C were less than those of groups A and B (p < 0.05), but there was no notable difference among groups at the postoperative 3-month and 1-year follow-ups (p > 0.05).

Conclusions

MIS-TKA in obese patients showed satisfactory clinical and radiological results without significant difference in surgical results compared to nonobese patients.

Mid-term survivorship of cruciate-retaining versus posterior-stabilized total knee arthroplasty using modular mini-keel tibial implants

Background

Reports of diverse outcomes in modular mini-keel tibial componentry for total knee arthroplasty (TKA) have raised concerns about early aseptic loosening. Cruciate-retaining (CR) prostheses, using mini-keel implants, have yet to be reported and compared to posterior-stabilizing (PS) designs.

Methods

A retrospective, case-matched study of 91 consecutive TKAs (n = 46 CR; n = 45 PS prostheses), using modular mini-keel tibial componentry with a 45-mm drop down stem extension, was conducted. The Knee Society Score functional survey, radiographic analysis including alignment and periprosthetic radiolucency, TKA prosthesis longevity, and surgical complications were reported and compared between CR and PS groups.

Results

The Knee Society Score at 5-year follow-up averaged 81.67 ± 11.97 and 80.12 ± 14.16 in the CR and PS groups, respectively (p = 0.29). The femorotibial angle averaged 5.85° ± 2.62° and 5.85° ± 3.27° valgus in the CR and PS groups, respectively (p = 0.60). The average tibial component angle was 0.46° ± 1.6° and 0.61° ± 1.3° varus in the CR and PS groups, respectively (p = 0.30); posterior inclination averaged 2.28° ± 2.36° and 1.93° ± 2.72° in the CR and PS groups, respectively (p = 0.51). Radiolucency was noted in 17 zones of the CR group and in 9 zones of the PS group (p = 0.24). Three TKAs required further surgery: one locking plate fixation for a periprosthetic tibial fracture (PS group) and two revision TKAs (one CR infection and one PS fracture).

Conclusion

Modular mini-keel tibial components showed good reliability and results with both CR and PS prostheses in minimally invasive surgery TKA.

Mid-term survivorship of Mini-keel™ versus Standard keel in total knee replacements: Differences in the rate of revision for aseptic loosening

INTRODUCTION

To reduce the size of the surgical incision, modular mini-keel tibial components have been developed with or without extensions for the Nexgen™ MIS Tibial Component. Although a smaller component could theoretically result in defective fixation, this has never been evaluated in a large comparative series. Thus, we performed the following case control study to: (1) evaluate intermediate-term survival of a modular "mini-keel" tibial component compared to a reference standard keel component from the same line of products (Nexgen LPS-Flex Tibial Component, Zimmer); (2) to identify any eventual associated factors if the frequency of loosening was increased.

HYPOTHESIS

The rate of revision for aseptic tibial loosening is comparable for both components.

MATERIALS AND METHODS

This comparative, retrospective, single center series of 459 consecutive total knee arthroplasties (TKA) was performed between 2007 and 2010: with 212 modular "mini-keel" (MK) tibial components and 247 "standard" (S) components. Survival, rate of revision for aseptic tibial loosening and identification of a radiolucent line were analyzed at the final follow-up.

RESULTS

After a median follow-up of 5years, the rate of revision for tibial aseptic loosing was significantly higher in the MK group with 12 cases (5.7%) and 4 cases in the S group (1.6%) (P=0.036). The use of the MK component appears to be a prognostic factor for surgical revision (hazard ratio=3.86 (1.23-11.88), P=0.02) but not for the development of a radiolucent line (HR=1.75 (0.9-3.4), P=0.097). The mean delay before revision was 38months (8-64) in the MK group and 15.2months (8-22) in the S group (P=0.006). Individual factors, such as gender, body mass index (BMI) and pre- or postoperative alignment were not prognostic factors for revision or radiolucent lines.

CONCLUSION

The modular "mini-keel" tibial component was associated with a greater risk of revision for tibial component loosening.

LEVEL OF EVIDENCE

Case control study, III.

Factors for Assessing the Effectiveness of Early Rehabilitation after Minimally Invasive Total Knee Arthroplasty: A Prospective Cohort Study

The effectiveness of current rehabilitation programs is supported by high-level evidence from the results of randomized controlled trials, but an increasing number of patients are not discharged from the hospital because of the schedule of the critical path (CP). The present study aimed to determine which factors can be used to assess the effectiveness of early rehabilitation. We enrolled 123 patients with medial knee osteoarthritis (OA) who had undergone unilateral minimally invasive total knee arthroplasty for the first time. The following factors were assessed preoperatively: the maximum isometric muscle strength of the knee extensors and flexors, maximum knee and hip joint angle, pain, 5-m maximum walking speed, sex, age, body mass index, exercise habits, Kellgren-Lawrence grade, femorotibial angle, failure side (bilateral or unilateral knee OA), and functional independence measure. We re-evaluated physical function (i.e., muscle strength, joint angle, and pain) and motor function (5-m maximum walking speed) 14 days postoperatively. Changes in physical function, motor function (5-m maximum walking speed), and number of days to independent walking were used as explanatory variables. The postoperative duration of hospitalization (in days) was used as the dependent variable in multivariate analyses. These analyses were adjusted for sex, age, body mass index, exercise habits, Kellgren-Lawrence grade, femorotibial angle, failure side, and functional independence measure. The duration of hospitalization was significantly affected by the number of days to independent walking (p < 0.001, β = 0.507) and a change in the 5-m maximum walking speed (p = 0.016, β = -0.262). Multiple regression analysis showed that the radiographic knee grade (p = 0.029, β = 0.239) was a significant confounding factor. Independent walking and walking speed recovery were considered to reduce the duration of hospitalization. Therefore, these indices can be used to assess the effectiveness of early rehabilitation.