Accuracy of implant positioning for minimally invasive total knee arthroplasty in patients with severe varus deformity

The accuracy of an extramedullary femoral cutting system in total knee arthroplasty in patients with severe coronal femoral bowing: a radiographic study

BACKGROUND

Intramedullary (IM) femoral alignment instrument is imprecise for the coronal alignment in total knee arthroplasty (TKA) in patients with severe lateral bowing of the femur, while the extramedullary (EM) alignment system does not depend on the structure of the femoral medullary cavity. The aim of this retrospective study was to compare the accuracy of postoperative limb alignment with the two femoral alignment techniques for patients with severe coronal femoral bowing.

METHODS

From January 2017 to December 2019, patients with end-stage knee osteoarthritis and coronal femoral bowing angle (cFBA) ≥ 5° who underwent total knee arthroplasty TKA at our institution were enrolled in the study. The postoperative hip-knee-ankle (HKA) alignment, femoral and tibial component alignment between the IM group and the EM group were compared on 5° ≤ cFBA < 10° and cFBA ≥ 10°.

RESULTS

In patients with 5° ≤ cFBA < 10°, no significant differences were observed in the EM group and IM group, including preoperative and postoperative parameters. However, when analyzing the patients with cFBA ≥ 10°, we found a significant difference in postoperative HKA (4.51° in the IM group vs. 2.23°in the EM group, p < 0.001), femoral component alignment angle (86.84° in the IM group vs. 88.46° in the EM group, p = 0.001) and tibial component alignment angle (88.69° in the IM group vs. 89.81° in the EM group, p = 0.003) between the two groups. Compared to the EM group, the IM group presents a higher rate of outliers for the postoperative HKA and femoral components.

CONCLUSIONS

The study showed that severe lateral bowing of the femur has an important influence on the postoperative alignment with the IM femoral cutting system. In this case, the application of EM cutting system in TKA will perform accurate distal femoral resection and optimize the alignment of lower limb and the femoral component.

High and Varied Anterior Condyle of the Distal Femur Is Associated with Limited Flexion in Varus Knee Osteoarthritis

OBJECTIVE

This study aimed to evaluate variations in anterior condylar height (ACH) of the distal femur in varus knee osteoarthritis and evaluate the association between ACH and knee flexion.

DESIGN

Computed tomography (CT) images of 171 knees (143 patients; age 73.7 ± 8.3 years; 132 females, 39 males) with symptomatic primary knee osteoarthritis and varus alignment undergoing primary total knee arthroplasty, unilateral knee arthroplasty, or high tibial osteotomy were evaluated. Several other anatomic parameters were measured on CT or radiography. The ACH and knee flexion correlation was analyzed, and factors contributing to knee flexion were determined using multivariable regression analysis.

RESULTS

Medial ACH (mean, 8.1 mm; range, -2.8 to 19.9 mm) was smaller (P < 0.001) but more variable (F = 1.8, P < 0.001) than lateral ACH (mean, 10.7 mm; range, 3.6-18.3 mm). Medial ACH was moderately correlated with flexion (r = -0.44, 95% confidence interval [CI], -0.55 to -0.32), whereas lateral ACH was weakly correlated (r = -0.38; 95% CI, -0.50 to -0.25). On multivariable linear regression analysis of knee flexion, body mass index (B [partial regression coefficient] = -1.1), patellofemoral Kellgren-Lawrence grade (B = -4.3), medial ACH (B = -1.2), medial posterior condylar offset (B = 1.2), age (B = -0.4), and varus alignment (B = -0.6) remained significant independent variables (adjusted R² = 0.35).

CONCLUSIONS

Wide variation and anteriorization of the anterior condyle of the distal femur was observed in advanced osteoarthritis, as an independent determinant of limited knee flexion.

Lateral Coronal Bowing of Femur and/or Tibia Amplifies the Varus Malalignment of Lower Limb as well as Increases Functional Disability in Patients with Knee Osteoarthritis

PURPOSE

In the present study, we aimed at assessing the effect of femoral and tibial coronal bowing on varus malalignment and Oxford knee score (OKS) at different grades of knee osteoarthritis (OA).

MATERIALS AND METHODS

This prospective observational study was conducted at a tertiary referral centre in New Delhi, India. Consecutive patients presenting to the "knee OA" outpatient clinics were invited to take part in the study conducted over a 12-month period. All consented patients underwent long-leg standing alignment radiographs using standardised technique and patient reported knee pain and function were recorded using Oxford knee score. The following radiological parameters were measured from weight-bearing long-leg radiographs of 824 varus aligned limbs via a morphometric software (Matlab R2009a) (1) hip-knee-ankle angle (HKAA), (2) femoral bowing, (3) tibial bowing. The knees were graded according to Kellegren and Lawrence grade (K&L) and OKS was recorded. 3 groups of HKAA were made based on the angle, A (0° to - 3°), B (- 3° to - 10°) and C (< - 10°). Both the femoral and tibial bow were also categorized into three groups depending upon the angle; in-range (- 2° to + 2°), varus (< - 2°), valgus (> + 2°).

RESULTS

The mean (± SD) of HKAA, femoral bow and tibial bow of the whole cohort was - 6.97° ± 5.64°, - 1.54° ± 4.31° and - 1.96° ± 3.5°, respectively. An increase in the lateral bow of both femur and tibia was seen with an increase in the severity of OA. A consequent increase in the varus malalignment was observed with an increase in the lateral bow of both femur as well as the tibia at all grades of OA, with significant correlation observed between HKAA with Femoral bowing and HKAA with tibial bowing. The mean OKS for femoral bow, in-range, varus and valgus was 30.6 ± 11.5, 21.3 ± 11.5 and 35.3 ± 11.4, respectively, and for tibial bow, in-range, varus and valgus was 27.6 ± 11.5, 26. ± 11.5 and 28 ± 11.4, respectively. The difference in the mean OKS was observed to be significant when the varus bow group was compared to in range as well as valgus group (p < 0.01) for both femur and tibia for all the grades of OA.

CONCLUSION

The present study shows a significant correlation between varus malalignment and the bowing of extremities. Varus coronal bowing of both femur and tibia were seen to have significantly lower mean OKS as compared to valgus bowing or in-range bowing at all grades of knee OA.

Influence of coronal bowing on the lower alignment and the positioning of component in navigation and conventional total knee arthroplasty

BACKGROUND

Coronal alignment is an important factor for the function and longevity of total knee arthroplasty (TKA). Coronal bowing of the lower extremity is common among Asians and it may pose a risk for malalignment of the lower leg and malposition of component.

HYPOTHESIS

We hypothesized that coronal bowing itself has a risk for malalignment of the lower leg and malposition of femoral/tibial components and that navigation TKA is beneficial for patients with coronal bowing. We investigated the incidence of femoral/tibial bowing in patients treated with TKA and compared the radiographic parameters between the navigation group and the conventional group. Additionally, the influence of coronal bowing on these radiographic parameters was investigated.

MATERIALS AND METHODS

We enrolled 35 patients with knee osteoarthritis and 70 bilateral simultaneous TKAs. The patients underwent TKA with the use of a computer tomography-free navigation in one knee and conventional TKA in the contralateral knee. Preoperative coronal bowing were measured, and the subjects were divided into 2 subgroups, i.e. the bowing group and the non-bowing group. Lateral bowing was expressed as plus (+) and medial bowing was expressed as minus (-). Various radiographic parameters, including coronal bowing, lower leg alignment, component position, and outliers were compared between the navigation group and the conventional group.

RESULTS

Femoral bowing varied from -7.4° to 10.9° with an average of 3.0°. Tibial bowing varied from -4.1° to 4.6° with an average of 0.4°. The femoral component was placed more properly in the navigation group. Number of outlier regarding to the coronal femoral component angle to the femoral mechanical axis was 14 cases (37.8%) in the bowing group and 6 cases (18.2%) in the non-bowing group (P=0.04).

DISCUSSION

In conclusion, coronal femoral bowing has an important effect on femoral bone cut in TKA. The navigated TKA was more consistent than conventional TKA in aiding proper alignments of femoral component.

LEVEL OF EVIDENCE

Level II, comparative prospective study.

Radiologic Outcomes According to Varus Deformity in Minimally Invasive Surgery Total Knee Arthroplasty

PURPOSE

To identify the accuracy of postoperative implant alignment in minimally invasive surgery total knee arthroplasty (MIS-TKA), based on the degree of varus deformity.

MATERIALS AND METHODS

The research examined 627 cases of MIS-TKA from November 2005 to December 2007. The cases were categorized according to the preoperative degree of varus deformity in the knee joint in order to compare the postoperative alignment of the implant: less than 5° varus (Group 1, 351 cases), 5° to less than 10° varus (Group 2, 189 cases), 10° to less than 15° varus (Group 3, 59 cases), and 15° varus or more (Group 4, 28 cases).

RESULTS

On average, the alignment of the tibial implant was 0.2±1.4°, 0.1±1.3°, 0.1±1.6°, and 0.3±1.7° varus, and the tibiofemoral alignment was 5.2±1.9degrees, 4.7±1.9°, 4.9±1.9°, and 5.1±2.0° valgus for Groups 1, 2, 3, and 4, respectively, in the preoperative stage, indicating no difference between the groups (p>0.05). With respect to the accuracy of the tibial implant alignment, 98.1%, 97.6%, 87.5%, and 86.7% of Groups 1, 2, 3, and 4, respectively, had 0±3° varus angulation, demonstrating a reduced level of accuracy in Groups 3 and 4 (p<0.0001). There was no difference in terms of tibiofemoral alignment, with 83.9%, 82.9%, 85.4%, and 86.7% of each group, respectively, showing 6±3° valgus angulation (p>0.05).

CONCLUSION

Satisfactory component alignment was achieved in minimally invasive surgery in total knee arthroplasty, regardless of the degree of varus deformity.

Effects of Reduction Osteotomy on Gap Balancing During Total Knee Arthroplasty for Severe Varus Deformity

This study aimed to assess the effects of down-sizing and lateralizing of the tibial component (reduction osteotomy) on gap balancing in TKA, and the clinical feasibility of an uncemented modular trabecular metal tibial tray in this technique. Reduction osteotomy was performed for 39 knees of 36 patients with knee OA with a mean tibiofemoral angle of 21° varus. In 20 knees, appropriate gap balance was achieved by release of the deep medial collateral ligament alone. Flexion gap imbalance could be reduced by approximately 1.7° and 2.8° for 4-mm osteotomy and 8-mm osteotomy, respectively. Within the first postoperative year, clinically-stable tibial component subsidence was observed in 9 knees, but it was not progressive, and the clinical results were excellent at a mean follow-up of 3.3 years.

Total knee arthroplasty in patients with substantial deformities using primary knee components

PURPOSE

Although advocated for severe varus and valgus deformities, constrained implant designs are associated with a number of disadvantages in total knee arthroplasty (TKA). Combining a minimally invasive surgical approach with an interchangeable posterior stabilized (PS) implant design may allow adequate soft tissue balancing with a minimal amount of constraint and without residual instability.

METHODS

Retrospectively 51 patients operated with the minimally invasive far medial subvastus approach for severe varus or valgus deformity, who underwent primary TKA with a fully interchangeable PS implant (Vanguard, Biomet Inc., Warsaw IN, USA) between 2009 and 2013 were examined. Soft tissue releases was performed using a piecrust needling technique. Preoperative alignment and surgical parameters were collected for all patients. All patients underwent preoperative and follow-up radiographic assessment and completed a battery of clinical assessments.

RESULTS

All procedures were performed successfully, with alignment improving from a preoperative mean (SD) varus deformity of 165° (3°) and a mean (SD) valgus deformity of 196° (4.5°) to an overall mean (SD) postoperative mechanical alignment of 179.5° (3.0°). Nine patients had postoperative varus, while three patients had a postoperative valgus deviation from neutral alignment >3°. The mean change in joint line position in extension was -0.0 ± 0.6 mm. Clinical scores at final follow-up were excellent for both groups.

CONCLUSIONS

Good TKA outcomes can be achieved in patients with substantial varus or valgus deformities using a combination of a minimally invasive far medial subvastus approach, interchangeable PS implants and soft tissue releases with a piecrust needling technique.

LEVEL OF EVIDENCE

III.

Factors affecting the achievement of Japanese-style deep knee flexion after total knee arthroplasty using posterior-stabilized prosthesis with high-flex knee design

BACKGROUND

Achievement of very deep knee flexion after total knee arthroplasty (TKA) can play a critical role in the satisfaction of patients who demand a floor-sitting lifestyle and engage in high-flexion daily activities (e.g., seiza-sitting). Seiza-sitting is characterized by the knees flexed >145º and feet turned sole upwards underneath the buttocks with the tibia internally rotated. The present study investigated factors affecting the achievement of seiza-sitting after TKA using posterior-stabilized total knee prosthesis with high-flex knee design.

METHODS

Subjects comprised 32 patients who underwent TKA with high-flex knee prosthesis and achieved seiza-sitting (knee flexion >145º) postoperatively. Another 32 patients served as controls who were capable of knee flexion >145º preoperatively, but failed to achieve seiza-sitting postoperatively. Accuracy of femoral and tibial component positions was assessed in terms of deviation from the ideal position using a two-dimensional to three-dimensional matching technique. Accuracies of the component position, posterior condylar offset ratio and intraoperative gap length were compared between the two groups.

RESULTS

The proportion of patients with >3º internally rotated tibial component was significantly higher in patients who failed at seiza-sitting (41 %) than among patients who achieved it (13 %, p = 0.021). Comparison of intraoperative gap length between patient groups revealed that gap length at 135º flexion was significantly larger in patients who achieved seiza-sitting (4.2 ± 0.4 mm) than in patients who failed at it (2.7 ± 0.4 mm, p = 0.007). Conversely, no significant differences in gap inclination were seen between the groups.

CONCLUSIONS

From the perspective of surgical factors, accurate implant positioning, particularly rotational alignment of the tibial component, and maintenance of a sufficient joint gap at 135º flexion appear to represent critical factors for achieving >145º of deep knee flexion after TKA.

Mini-midvastus total knee arthroplasty in patients with severe varus deformity

Patients with severe varus deformity of the knee (≥15° varus) usually are not considered good candidates for minimally invasive total knee arthroplasty (TKA). The goal of this study was to retrospectively investigate outcomes in patients with severe varus deformity after minimally invasive TKA. A study group of 52 patients with a tibiofemoral mechanical axis of 195° or greater was compared with a matched control group of 55 patients with a tibiofemoral mechanical axis of less than 195°. Clinical and radiographic evaluations according to the American Knee Society rating system were obtained preoperatively and postoperatively, and postoperative patient satisfaction in the 2 groups was compared. All patients were followed at a mean of 3 years (range, 2-5 years). Preoperatively, clinical knee and function scores and range of motion were inferior in the study group compared with the control group (P<.001). However, at the latest follow-up, both groups of patients were satisfied with the clinical results, and no significant differences were found in the knee and function scores (P>.05). Radiographic evaluation showed no differences in the mechanical axis, femoral component valgus angle, and tibial component valgus angle, and all outliers of the radiographic parameters between the 2 groups postoperatively (P >.05). The study results showed that mini-midvastus TKA did not result in more inaccurate implant positioning in patients with severe varus deformity of the knee. The clinical outcome in the group with severe varus was comparable to that in the group with less severe varus

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

Purpose

To evaluate the minimum 5-year mid-term clinical and radiological results of minimally invasive surgery total knee arthroplasty (MIS-TKA) using a mini-keel modular tibia component.

Materials and Methods

We retrospectively evaluated 254 patients (361 cases) who underwent MIS-TKA between 2005 and 2006. The latest clinical and radiological assessments were done in 168 cases that had been followed on an outpatient basis for more than 5 postoperative years. Clinical results were assessed using the Hospital for Special Surgery (HSS) score and Knee Society score. Radiological evaluation included measurements of knee alignment.

Results

The average postoperative knee range of motion and HSS score were 134.3°±12.4° and 92.7°±7.0°, respectively. The average postoperative femorotibial angle and tibial component alignment angle were 5.2°±1.7° valgus and 90.2°±1.6°, respectively. The average tibial component posterior inclination was 4.8°±2.1°. The percentage of cases with tibial component alignment angle of 90°±3° was 96.1%, and that with the femorotibial angle of 6°±3° valgus was 94.0%. Radiolucent lines were observed in 20 cases (12.0%): around the femur, tibia, and patella in 14 cases, 10 cases, and 1 case, respectively. However, they were less than 2 mm and non-progressive in all cases. The survival rate was 99.4% and there was no implant-related revision.

Conclusions

MIS-TKA using a mini-keel modular tibial plate showed satisfactory results, a high survival rate, and excellent clinical and radiological results in the mid-term follow-up.

Effects of four different surgical approaches on intra-operative joint gap in posterior-stabilized total knee arthroplasty

PURPOSE

The effects of surgical approaches and patellar positions on joint gap measurement during total knee arthroplasty (TKA) remain unclear. We hypothesized that joint gap changes with different knee flexion angles would not be consistent within four different approaches and two different patellar positions.

METHODS

This study enrolled 80 knees undergoing posterior-stabilized TKA. For 60 varus knees, parapatellar, midvastus, and subvastus approaches were used in 20 knees each. For 20 valgus knees, a lateral subvastus approach was used. Component gap length and inclination were measured intra-operatively using a specific tensor device under 40 lb with the patella reduced or shifted laterally, at 0°, 45°, 90°, and 135° of knee flexion.

RESULTS

Mean gap lengths at 45° and 90° of knee flexion were significantly larger with the parapatellar approach than with midvastus or lateral subvastus approaches (P < 0.05). Regarding gap inclination, varus angle increased linearly through the entire arc of flexion in all four approaches. When the patella was shifted laterally, gap lengths at 45°, 90°, and 135° were significantly reduced compared with those for the patella reduced in the subvastus approach, whereas gap length was constant in the parapatellar approach, regardless of patellar position.

CONCLUSION

Joint gap kinematics was not consistent within four different approaches and two different patellar positions. Relatively large gaps at 45° and 90° were unique features for the parapatellar approach. Surgeons should be aware that the flexion gap is reduced when the patella is shifted laterally in vastus medialis-preserving approaches such as the subvastus approach.

LEVEL OF EVIDENCE

II.

Modular tibial plate for minimally invasive total knee arthroplasty

PURPOSE

Aim of the study was to evaluate the clinical and radiological results of a modular tibial plate purposely designed for minimally invasive total knee arthroplasty.

METHODS

We prospectively assessed the results of 200 primary total knee replacements performed through a minimally invasive approach using a dedicated modular tibial plate, a posterior stabilized knee prosthesis, and a fixed bearing in 175 patients (139 women and 36 men), undergoing surgery between 2005 and 2009 presenting knee osteoarthritis. Median age at the time of surgery was 69 years (52-88).

RESULTS

No patients were lost at follow-up. 3 implants underwent revision. At a mean 3 years (1-5 years) follow-up, the HHS and KSS score showed a significant improvement, increasing, respectively, from a median value of 35-95 (78-100) and from 31 points in the "knee" and 45 points in the "function" score to a median of 95 (83-100) and 94 (81-100). Using the Kaplan-Meier method, the survival rate at 5 years was 97.9% with a 95% confidence interval.

CONCLUSION

The implant showed good results in either clinical or radiological assessment at a short/midterm follow-up with a high survival rate.

LEVEL OF EVIDENCE

Therapeutic study, Level IV.

[Total knee arthroplasty for rheumatoid arthritis]

A total of 150,000 primary total knee arthroplasties are performed in Germany each year. There is only a limited amount of evidence-based data available on possible surgery-related differences between osteoarthritis (OA) and rheumatoid arthritis (RA) of the knee joint. The following review summarizes the recent literature on total knee arthroplasty with a focus on special features of RA patients.

Soft tissue balance measurement in minimal incision surgery compared to conventional total knee arthroplasty

PURPOSES

Minimal incision surgery (MIS) total knee arthroplasty (TKA) is widely promoted as a possible improvement over conventional TKA, and accurate implantations have recently been reported using navigation systems. However, soft tissue balance during MIS-TKA remains challenging. Therefore, in this report, joint gap (component gap) and ligament balance (varus angle) were assessed during MIS-TKA using a tensor, which enables soft tissue balance assessment with a reduced patellofemoral joint and femoral component in place.

METHODS

Results were compared to those of conventional TKA. Posterior stabilized TKA were performed in 50 knees (25 knees: MIS-TKA using quadriceps-sparing approach; 25 knees: conventional TKA using medial parapatellar approach) with varus osteoarthritis. Component gap and varus angle were measured using the tensor with a reduced patellofemoral joint at 0, 10, 45, 90, and 135°.

RESULTS

Whereas the component gap in MIS-TKA was significantly larger through the entire arc of flexion compared with conventional TKA, the pattern of joint looseness showed no difference between the two procedures. The varus angle in MIS-TKA was significantly larger than that in conventional TKA at 0, 90, and 135° of knee flexion.

CONCLUSIONS

MIS-TKA may lead to ligament imbalance due to the difficulties induced by a limited working space. Understanding this pattern allows surgeons to be able to adjust the soft tissue balance more accurately and thereby expect a better post-operative outcome even in MIS-TKA.

Clinical and radiographic outcomes of minimally invasive total knee arthroplasty through a lateral approach

PURPOSE

With increasing confidence and surgical experience, minimally invasive surgery (MIS) in total knee arthroplasty (TKA) is now being applied to more complicated cases. The present study assessed the feasibility of MIS-TKA using a lateral approach for valgus knees.

METHODS

Subjects comprised 26 patients with valgus knees who underwent MIS-TKA using a lateral subvastus approach. Five cases required a 1-cm snip of vastus lateralis obliquus, to shift the patella medially without eversion. Clinical scores and radiographic parameters of lateral MIS-TKA were examined and compared with those of 26 medial MIS-TKAs matched for preoperative patient characteristics.

RESULTS

The lateral MIS-TKA group showed slightly longer operative time and larger skin incision than the medial MIS-TKA group. Nevertheless, myoglobin index and pain on a visual analog scale on postoperative day 7 were significantly lower in the lateral MIS-TKA group than in the medial MIS-TKA group. Postoperative improvement of clinical scores was quite comparable between lateral and medial MIS-TKA groups. Radiographic assessment revealed that tibiofemoral mechanical axis aligned within ±3° from ideal in 24 of 26 patients after lateral MIS-TKA. MIS technique-related complications occurred in only 1 patient presenting with subsidence of the tibial component, due to malpositioning of the tibial component.

CONCLUSION

From the perspectives of postoperative pain, clinical scores, radiographic accuracy, and postoperative complication rate, lateral MIS-TKA achieved comparable or superior results to medial MIS-TKA. This technique may offer a promising technical option that can be utilized for most patients with valgus knee deformity.