Risk factors of hyperextension and its relationship with the clinical outcomes following mobile-bearing total knee arthroplasty

Isolated Polyethylene Insert Exchange for Instability after Total Knee Arthroplasty: Comparable Survival Rates and Range of Motion and Improved Clinical Scores Regardless of Hyperextension

Background

Isolated polyethylene insert exchange (IPIE) has not been established as a treatment option for hyperextension instability after primary total knee arthroplasty (TKA). The purpose of the study was to evaluate the survival rate and clinical outcomes of IPIE for the treatment of instability with or without hyperextension after TKA.

Methods

This study retrospectively reviewed 46 patients who underwent IPIE for symptomatic prosthetic knee instability by dividing them into 2 groups based on the presence of hyperextension (without for group I and with for group IH). Patient demographics, clinical scores, radiographic data, range of motion (ROM), and surgical information were collected. Clinical failure was defined as a subsequent surgery following IPIE for any reason. The survival rate of IPIE and differences in demographics, clinical scores, and ROM were compared.

Results

There were 46 patients (91% were women) with an average age of 70.1 years and a mean follow-up of 44.8 months. The average time between primary TKA and IPIE surgery was 6.5 ± 4.2 years, and during IPIE, 2 out of the 8 cruciate-retaining inserts were converted to "deep-dish" ultracongruent inserts while the insert thickness increased from 11.9 ± 1.8 mm to 17.1 ± 3.1 mm. After IPIE surgery, a significantly thicker tibial insert was used in the group with hyperextension (15.39 ± 2.4 mm for group I, 18.3 ± 2.9 mm for group IH; p < 0.001 by independent t-test), and no significant differences were observed in the ROM and clinical scores before and after IPIE between the 2 groups. The overall survival rate for IPIE was 83% at 5 years and 57% at 10 years, and there were no statistically significant differences between the groups using the Cox proportional hazards regression model.

Conclusions

IPIE demonstrated an overall survival rate of 83% at 5 years with no difference in the recurrence of instability regardless of hyperextension. This study highlighted the effectiveness of using thicker inserts to resolve instability without significant differences in the ROM or clinical scores between the groups, suggesting its potential as a decision-making reference for surgeons.

Sagittal Alignment in Total Knee Arthroplasty: Are There Any Discrepancies Between Robotic-Assisted and Manual Axis Orientation?

BACKGROUND

Sagittal alignment determines the extension and flexion of knee prostheses in total knee arthroplasty (TKA). The definition of the sagittal axes may be different between the Mako TKA system (Stryker) and the conventional manual intramedullary approach. Whether there is any discrepancy between the 2 approaches has not been well studied.

METHODS

We retrospectively analyzed 60 full-length computed tomographic (CT) scans of the lower extremities of 54 patients. The femur and tibia were modeled by using Mimics (Materialise). The Mako mechanical axes were determined according to the Mako TKA Surgical Guide. The manual intramedullary axes were determined according to the central axis of the tibial proximal and femoral distal medullary cavities. The femoral, tibial, and combined angular discrepancies were measured in the sagittal plane.

RESULTS

On the femoral side, the Mako mechanical axis was more likely to be located in an extended position relative to the manual intramedullary axis (56 of 60 knees). The median angular discrepancy was 2.46° (interquartile range [IQR], 1.56° to 3.43° [range, -1.06° to 5.24°]). On the tibial side, the Mako mechanical axis was likely to be located in a flexed position relative to the manual intramedullary axis (57 of 60 knees). The median angular discrepancy was 2.40° (IQR, 1.87° to 2.84° [range, -0.79° to 4.20°]). The angular discrepancy of the femoral-tibial sagittal angle was 4.63° (IQR, 3.71° to 5.64° [range, 1.20° to 9.02°]).

CONCLUSIONS

Compared with manual TKA, the Mako system is more likely to result in a decreased posterior tibial slope and extension of the femoral prosthesis. It may also influence the evaluation of lower-extremity extension and flexion. When using the Mako system, special attention should be given to these discrepancies.

LEVEL OF EVIDENCE

Therapeutic Level IV . See Instructions for Authors for a complete description of levels of evidence.

Risk factors of de novo hyperextension developed after posterior cruciate ligament substituting total knee arthroplasty: a matched case-control study

PURPOSE

To investigate factors contributing to the de novo hyperextension after posterior cruciate ligament substituting (PS) total knee arthroplasty (TKA).

METHODS

Through a retrospective case-control study, de novo hyperextension patients were compared with patients without hyperextension after primary PS TKA. Eighty-five hyperextension patients were compared with 85 patients in a control group matched by age, sex, surgeon and implant. The clinical and radiographic parameters, including the mechanical axis (MA), joint line convergence angle (JLCA), posterior tibial slope angle (PTSA), posterior condylar offset (PCO), and the gamma angle, were evaluated preoperatively and immediate postoperatively. Comparisons between the two groups and logistic regression analysis were performed to investigate factors contributing to de novo hyperextension.

RESULTS

Among the clinical factors, preoperative flexion contracture was less (5° ± 6° vs. 11° ± 6°, p < 0.001) and the range of motion was greater (125° ± 12° vs. 118° ± 5°, p = 0.041) in the de novo hyperextension group than in the control group. Among the radiographic parameters, preoperative and postoperative JLCA were greater (8.1° ± 4.4° vs. 6.1° ± 3.5°, p < 0.001, 1.0° ± 1.3° vs. 0.2° ± 0.8°, p = 0.002, respectively), postoperative PTSA was greater (3.7° ± 2.0° vs. 3.3° ± 1.6°, p < 0.001) and preoperative and postoperative PCO were less in the hyperextension group than in the control group (26.3 mm ± 3.3 mm vs. 29.1 mm ± 3.2 mm, p < 0.001, 26.4 mm ± 3.2 mm vs. 29.1 mm ± 3.0 mm, p < 0.001, respectively), whereas, change in PCO was greater in the hyperextension group (1.1 mm ± 7.7 mm vs. - 0.1 mm ± 3.3 mm, p < 0.001). In multivariate analysis, the degree of medial soft tissue release [odds ratio (OR) 2.83, p = 0.003], flexion contracture [OR 0.86, p = 0.028], postoperative JLCA [OR 2.45, p = 0.004], preoperative PCO and a change in PCO [OR 0.74, p = 0.002, OR 1.89, p = 0.001, respectively] were the factors associated with de novo hyperextension.

CONCLUSIONS

An increased degree of medial soft tissue release, small preoperative flexion contracture, increased postoperative JLCA, decreased preoperative PCO and increased change in PCO were risk factors of de novo hyperextension.

LEVEL OF EVIDENCE

III.

Hyperextension following two different designs of fixed-bearing posterior-stabilized total knee arthroplasty

PURPOSE

Hyperextension after total knee arthroplasty (TKA) is related to worse functional outcomes. Among the reported predictive factors, it is unclear whether prosthesis design affects postoperative hyperextension. Hence, our objectives were to (1) compare time-dependent changes of the extension angle following multi-radius (MR) and single-radius (SR) TKA and (2) assess predictive factors for the hyperextension.

METHODS

In this study, consecutive 136 MR TKAs and consecutive 71 SR TKAs performed by a single surgeon were reviewed. The extension angle was evaluated by digitized full-extension lateral radiographs at preoperative, 3 months and at 1 and 2 years after TKA. A positive value was defined as hyperextension. A multiple regression analysis was used to determine predictive factors for the extension angle and the risk of hyperextension > 5°.

RESULTS

The postoperative extension angle of both groups gradually increased during the first 2 years and the SR group finally progressed with 4.04° greater extension than the MR group (p < 0.01). The incidence of hyperextension > 5° in the SR group was 18.3% and for the MR group, 7.4% (p = 0.02). However, the Oxford knee scores was nonsignificant different between the groups (p = 0.15). Preoperative extension angle, sagittal femoral component angle (SFA) and SR prosthesis were predictive factors for the extension angle at 2 years after TKA and were also associated with hyperextension > 5°.

CONCLUSIONS

The extension angle of the SR group became significantly more extended than that of the MR group during the first two years after TKA. Hence, ideal extension position immediately after SR TKA may be different from that of the MR TKA prosthesis. The preoperative extension angle, SFA and SR prosthesis were factors that were associated with postoperative hyperextension.

Gender-specific difference in the recurrence of flexion contracture after total knee arthroplasty

Background

Range of motion after total knee arthroplasty (TKA) can impact patients’ daily lives. Nevertheless, flexion contracture (FC) often recurs after TKA, even upon achieving full extension intraoperatively. This study aimed to evaluate the relationship among preoperative, intraoperative, and postoperative knee extension angles, and clarify the risk factor for postoperative FC.

Methods

One hundred forty-seven knees undergoing TKA using a navigation system were evaluated. We measured the pre- and postoperative (6 months after TKA) extension angles using a goniometer, and intraoperative (before and after TKA) extension angle using a navigation system; the correlation between these angles at each time point was evaluated.

Results

The mean preoperative, intraoperative (before and after TKA) and postoperative extension angles were -9.9°, -6.8°, -0.1°, and -2.0°. Regarding intraoperative extension angle after TKA, 58 knees showed ≤ 5° hyperextension and six knees showed > 5° hyperextension. At 6 months, no cases showed hyperextension and 105 knees showed full extension. The mean intraoperative extension angle after TKA in the postoperative full extension group was 0.4°. A significant correlation was found among extension angles at each point (p<0.01, respectively). However, the intraoperative extension angle after TKA correlated with the postoperative extension angle only in females. Contrarily, the recurrence rate of FC was significantly higher in males than in females (p<0.01).

Conclusion

Intraoperative extension angles significantly correlated with pre- and postoperative extension angles in TKA. Moreover, intraoperative mild (≤ 5°) hyperextension is acceptable for postoperative full extension. There was a gender-specific difference in correlation between intra- and postoperative knee extension angles.

Level of evidence

III.

Comparison of risk for postoperative hyperextension between cruciate retaining and posterior stabilized total knee arthroplasties

INTRODUCTION

The incidence of postoperative hyperextension and factors affecting hyperextension needs to be investigated separately for cruciate retaining (CR) and posterior stabilized (PS) total knee arthroplasties (TKAs), because the mechanism for preventing hyperextension is different according to the bearing design. The purpose of the study was to compare the incidence of postoperative hyperextension between CR and PS TKAs and analyze the factors affecting the postoperative hyperextension.

METHODS

Matched 213 CR and PS TKAs with Persona^® prosthesis were retrospectively reviewed. The preoperative demographics, clinical and radiographic knee condition, and pelvic incidence were similar between groups. Appropriate knee extension (0°-5°), confirmed with a goniometer, was achieved intraoperatively. The knee sagittal angle was radiographically measured preoperatively and at 2 years postoperative. The incidence of hyperextension (sagittal angle < - 5°) was investigated. The factors affecting the postoperative hyperextension were analyzed in terms of age, sex, preoperative mechanical axis, knee sagittal angle, postoperative posterior tibial slope (PTS), change of posterior femoral offset, and pelvic incidence.

RESULTS

The knee sagittal angle was not significantly different preoperatively between CR and PS TKAs. The postoperative knee sagittal angle was 2.9° in CR TKAs and 4.4° in PS TKAs (p = 0.004). The incidence of postoperative hyperextension was 11.7% (25/213) in CR TKAs and 4.2% (9/213) in PS TKAs (p = 0.007). The preoperative sagittal angle, postoperative PTS, and pelvic incidence were the significant factors affecting the postoperative hyperextension in CR TKAs (odds ratio 0.869, 2.205, and 1.045, respectively); the preoperative sagittal angle was only the significant factor in PS TKAs (odds ratio 0.857) CONCLUSIONS: Postoperative knee hyperextension occurred more frequently and was affected by more factors in CR TKAs than PS TKAs. Efforts to avoid hyperextension and closed observation are required in TKAs performed in patients with the risk factors.

LEVEL OF EVIDENCE

III.