Assessing coronal laxity in extension and flexion at a minimum of 10 years after primary total knee arthroplasty

Residual varus alignment after posterior-stabilized total knee arthroplasty limits medial soft tissue remodeling

BACKGROUND

Proper lower limb alignment and soft tissue balance are significant indicators to measure the success of total knee arthroplasty (TKA). Previous studies have confirmed that soft tissue relaxation around the knee after TKA will change over time; however, the relationship between lower limb alignment and soft tissue balance after TKA remains unclear. We studied (1) whether the change of soft tissue balance around the knee with time after posterior-stabilized (PS) TKA would affect the alignment of the lower limbs; (2) Whether the accuracy of lower limb alignment during PS TKA affects postoperative soft tissue remodeling.

METHODS

In this study, 100 patients were recruited after PS TKA. Among them, 50 patients with a hip knee ankle (HKA) angle of ≤  ± 3° were set as the neutral group, and 50 patients with an HKA angle of >  ± 3° were set as the deviation group. The imaging results measured the HKA angle before the operation as well as the HKA, varus, and valgus angles at 1, 3, 6, 12, and 24 months after TKA. Clinical assessment included range of motion (ROM), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Knee Society Score (KSS).

RESULTS

Eight people were excluded from the study. After the exclusion, the study enrolled 47 patients in the neutral group and 45 patients in the deviant group and were followed for up to 2 years. There was no statistical significance in mean varus angles as well as HKA angle changes during the follow-up phase of each groups (P > 0.05). The mean valgus angles of the patients in the neutral group group were 2.47°, 3.45°, 3.63°, 3.60° and 3.63°, and in the deviation group were 2.45° (P = 0.841), 2.88° (P < 0.001), 3.07° (P < 0.001), 3.06° (P < 0.001), and 3.10° (P < 0.001). ROM, WOMAC and KSS of the two groups were significantly improved after operation, with no difference between the two groups.

CONCLUSION

This study shows that whether the alignment is accurate or not in the early stage after TKA, the relaxation of the medial and lateral soft tissues of the knee joint change; however, this change will not significantly affect the alignment of the lower limbs. Postoperative residual varus deformity limits medial soft tissue remodeling.

LEVEL OF EVIDENCE

III.

The Correlation between Objective Ligament Laxity and the Clinical Outcome of Mechanically Aligned TKA

Instability is one of the causes of failure in total knee arthroplasty (TKA). The aim of this study was to analyze the correlation between objective ligament laxity and the clinical outcome of mechanically aligned TKA. Fifty-one knees in 47 patients were evaluated at a minimum follow-up of 6 months. The correlation between the angular displacement and functional scores (Knee Society Score and Knee Injury and Osteoarthritis Score) was analyzed. A negative correlation (p-value < 0.05) was observed between medial laxity ≥5° at 0, 30, 60, and 90° of flexion and the outcome measures. Lateral laxity did not correlate with the clinical outcome. At 30° of knee flexion, a total varus and valgus laxity ≥10° was related to poorer outcomes. The same amount of angular displacement did not influence the outcome in the other flexion angles. There was no difference in single-radius vs multi-radius implants in terms of medial and lateral laxity and clinical outcome. A valgus displacement ≥5° measured at 0, 30, 60, and 90 degrees of flexion correlated with an inferior clinical outcome. In contrast, the same amount of displacement measured on the lateral compartment did not influence the clinical outcome after TKA.

Difference in implant design affects midflexion rotational laxity in cruciate-retaining total knee arthroplasty: a computer navigation study

PURPOSE

This study aimed to compare midflexion rotational laxity between two different design concept models of cruciate-retaining total knee arthroplasty: symmetrical surface design of neutral joint line obliquity and asymmetrical surface design of varus joint line obliquity.

METHODS

Sixty-three knees that underwent cruciate-retaining total knee arthroplasty were evaluated. Manual maximum passive rotational stress without acceleration was applied to the knees under navigation monitoring. Pre-operative and post-operative internal and external rotational angles were measured at 30°, 45°, 60°, and 90° knee flexion.

RESULTS

The post-operative internal rotational laxity was significantly increased compared with pre-operative levels at 30°, 45°, 60°, and 90° flexion among all subjects (mean 9.7° vs 11.1°, 10.6° vs 11.6°, 11.2° vs 12.9°, and 13.2° vs 14.9°; p = 0.01, 0.04, 0.001, and 0.008, respectively). The post-operative external rotational laxity was significantly decreased compared to pre-operative levels at 30°, 45°, 60°, and 90° flexion among all subjects (mean 10.8° vs 6.8°, 12.5° vs 9.4°, 12.8° vs 10.0°, and 11.3° vs 9.5°; p < 0.0001, < 0.0001, < 0.0001, and 0.0008, respectively). The post-operative total rotational laxity significantly decreased, compared with pre-operative levels, at 30° and 45° flexion among all subjects (mean 20.4° vs 17.9°, and 23.1° vs 21.1°; p = 0.002 and 0.04, respectively). The post-operative total rotational laxity was significantly smaller in asymmetrically designed total knee arthroplasty than in symmetrically designed total knee arthroplasty at 30°, 45°, and 60° flexion (mean 19.3° vs 15.8°, 22.8° vs 18.7°, and 24.4° vs 20.8°; p = 0.03, 0.03, and 0.02, respectively), whereas no significant difference was observed at 90° flexion.

CONCLUSION

Compared to symmetrical surface design, asymmetrical surface design resulted in lower rotational laxity at the midflexion range in cruciate-retaining total knee arthroplasty.

LEVEL OF EVIDENCE

III.

Coronal Laxity at Flexion is Larger After Posterior-Stabilized Total Knee Arthroplasty Than With Cruciate-Retaining Procedures

BACKGROUND

It is unclear whether coronal stability differs between cruciate-retaining (CR) and posterior-stabilized (PS) total knee arthroplasty (TKA). The purpose of this study was to compare coronal laxity, radiological, and clinical outcomes between CR-TKA and PS-TKA.

METHODS

Seventy five CR-TKAs and 72 PS-TKAs with a minimum 2-year follow-up were retrospectively evaluated. Coronal laxity was assessed at knee extension and 80° of flexion on varus and valgus stress radiographs. Radiological evaluation included femoral-tibial angle, hip-knee-ankle angle, and positions of femoral and tibial components. Clinical evaluation included the modified Hospital for Special Surgery score, the Western Ontario and McMaster Universities Osteoarthritis index, and range of motion.

RESULTS

PS-TKA resulted in significantly larger varus, valgus, and total laxities at 80° flexion (P = .034, .031, and 0.001, respectively) compared with CR-TKA, while no significant difference was found at extension (P = .513, .964, and .658, respectively). No statistical difference was found in radiological and clinical outcomes between CR-TKA and PS-TKA, but the functional scores were slightly better in CR-TKA. There were adverse correlations between varus laxity at flexion and the Western Ontario and McMaster Universities Osteoarthritis index, the modified Hospital for Special Surgery score, and range of motion (r = 0.933, -0.229, -0.472, respectively).

CONCLUSION

Coronal laxity at 80° of flexion was larger after PS-TKA than CR-TKA. In addition, clinical outcomes were adversely affected by the larger varus laxity at flexion. Care should be taken to maintain the coronal stability, especially at flexion, during surgery to obtain better patient-reported outcomes.

LEVEL OF EVIDENCE

Level III.

Consistent femoral external rotation during weight-bearing knee flexion is associated with better patient-reported pain and mediolateral balance after total knee arthroplasty

BACKGROUND

Normal knees generally show consistent femoral external rotation during knee flexion, although knees that have had total knee arthroplasty exhibit various rotational patterns with less rotational angle. This study aimed to determine whether consistent femoral external rotation during weight-bearing knee flexion after total knee arthroplasty is associated with better patient-reported outcomes and mediolateral joint balance.

METHODS

A total of 40 total knee arthroplasty knees with a high-flexion posterior-stabilized prosthesis were divided into two groups based on their axial rotational kinematic pattern during squatting activity, and the clinical results including patient-reported outcomes and joint laxity were compared between the consistent external rotation group (20 knees) and the inconsistent external rotation group (20 knees). The unpaired Student's t-test or Welch's test were used for group comparison, and Fisher's exact test was applied for categorical data.

FINDINGS

"Pain at rest" and "Pain at first gait in the morning" measured using a numerical rating scale (/10) were significantly lower in the consistent external rotation group compared with those in the inconsistent external rotation group. "Pain during gait on flat surface" tended to be lower in the consistent external rotation group. Medial stability was obtained in both groups with significantly greater lateral laxity in extension in the inconsistent external rotation group.

INTERPRETATION

Total knee arthroplasty knees with consistent femoral external rotation during weight-bearing knee flexion exhibited better patient-reported pain and mediolateral soft tissue balance. Surgical procedures that control the mediolateral balance with medial stability would induce consistent femoral external rotation and improve patient-reported pain.

Characteristic kinematics of floor-sitting activities after posterior-stabilized total knee arthroplasty determined using model-based shape-matching techniques

BACKGROUND

Detailed kinematics of floor-sitting activities after total knee arthroplasty (TKA) have not been well explored. Knee kinematics of cross-legged sitting, seiza-sitting, and side-sitting after TKA were examined to clarify the differences in tibiofemoral kinematics of each activity.

METHODS

Subjects were 40 knees in 20 osteoarthritic patients who underwent bilateral TKA with a high-flexion fixed-bearing posterior-stabilized prosthesis. Dynamic radiographs of floor-sitting activities were taken, and the knee kinematics were compared among the three activities. The patients were also divided into two groups (possible/easy group and impossible/no-try group) for each activity, and group comparisons were conducted.

RESULTS

The maximum implant flexion angle was significantly greater in seiza-sitting. In valgus/varus rotation, seiza-sitting demonstrated neutral rotation, while cross-legged sitting showed varus of about 10°, and side-sitting exhibited valgus. In tibial internal/external rotation, seiza-sitting demonstrated a constant rotational angle, while cross-legged sitting showed tibial internal rotation with flexion, and side-sitting exhibited tibial external rotation with flexion. The kinematic pathway during deep flexion illustrated the medial pivot pattern in cross-legged sitting, a small amount of bicondylar rollback in seiza-sitting, and the weak lateral pivot pattern in side-sitting. A greater flexion angle was the important factor for the performance of each floor-sitting activity followed by varus laxity at 10° knee flexion.

CONCLUSIONS

This study successfully revealed characteristic kinematic patterns of TKA knees in three floor-sitting activities. Obtaining a greater knee flexion with adequate lateral laxity is the key to enhancing postoperative floor-sitting activities.

Retrieval Analysis of Cruciate-Retaining and Posterior-Stabilized Total Knee Arthroplasty and Correlations to Laxity and Wear

BACKGROUND

Total knee arthroplasty (TKA) with posterior-stabilized (PS) or posterior cruciate-retaining (CR) implants has high success rates and survivorship. However, it is uncertain how laxity and constraint are associated with long-term polyethylene wear under physiological conditions.

METHODS

To answer this question, we measured the laxity patterns of 47 harvested cadaver specimens with primary TKAs in a custom knee-testing machine at full extension and at 30°, 60°, and 90° of flexion. The wear patterns of the tibial inserts were assessed using a semiquantitative method which is a modified approach of that proposed by Hood et al in 1983.

RESULTS

Statistical analysis found that the PS TKA cohort had a statistically significant increase in varus laxity at 60° and 90° of flexion, as well as total coronal laxity at 60° of flexion when compared to the CR cohort. Furthermore, analysis demonstrated a significant correlation between increased PS coronal laxity and increased tibial wear, a trend that was not seen in the CR specimens.

CONCLUSION

Our findings suggest that greater laxity in flexion after primary TKA may increase the wear realized over time and that PS TKAs may be more susceptible due to the loss of support the PCL affords to the flexion space. Whether a CR or PS TKA is used, surgeons need to avoid the pitfalls that may create greater flexion laxity during the procedure to optimize long-term polyethylene wear.

Coronal and sagittal laxity affects clinical outcomes in posterior-stabilized total knee arthroplasty: assessment of well-functioning knees

PURPOSE

Both coronal and sagittal laxity of well-functioning knees after total knee arthroplasty (TKA) was examined, and the correlations between the joint laxity and the clinical outcomes were analyzed to clarify the adequate joint laxity for the prosthesis, and the relationship between the laxity and the outcomes.

METHODS

Forty well-functioning TKA knees with a high-flexion posterior-stabilized (PS) prosthesis were studied. All patients were diagnosed as having osteoarthritis with varus deformity and were followed up for 2 years or more. The coronal and sagittal laxity was assessed at extension and flexion, and the correlations between the joint laxity and the clinical outcomes were evaluated.

RESULTS

The varus and valgus laxity averaged 5.6 ± 1.8° and 3.6 ± 1.2° at 10° knee flexion, and 7.4 ± 5.1° and 3.6 ± 2.7° at 80° knee flexion, respectively, and the AP laxity at 30° and 75° knee flexion averaged 8.7 ± 3.6 mm and 6.6 ± 2.3 mm, respectively. Knee flexion angle correlated with the joint laxity, while the other outcomes including patient-reported pain and instability were adversely affected by the greater laxity.

CONCLUSIONS

This study exhibited the importance of consistent medial laxity both at extension and flexion, which averaged 3.6°. Care should be taken to maintain the medial stability and to obtain adequate laxity both at extension and flexion during surgery. A few degrees of medial tightness can be allowed to achieve excellent clinical results after TKA for preoperative varus knees.

LEVEL OF EVIDENCE

Therapeutic study, Level III.

Flexion Instability After Total Knee Arthroplasty

Flexion instability after total knee arthroplasty (TKA) is caused by an increased flexion gap compared with extension gap. Patients present with recurrent effusions, subjective instability (especially going downstairs), quadriceps weakness, and diffuse periretinacular pain. Manual testing for laxity in flexion is commonly done to confirm a diagnosis, although testing positions and laxity grades are inconsistent. Nonsurgical treatment includes quadriceps strengthening and bracing treatment. The mainstays to surgical management of femoral instability involve increasing the posterior condylar offset, decreasing the tibial slope, raising the joint line in combination with a thicker polyethylene insert, and ensuring appropriate rotation of implants. Patient outcomes after revision TKA for flexion instability show the least amount of improvement when compared with revisions for other TKA failure etiologies. Future work is needed to unify reproducible diagnostic criteria. Advancements in biomechanical analysis with motion detection, isokinetic quadriceps strength testing, and computational modeling are needed to advance the collective understanding of this underappreciated failure mechanism.

Association between bone mineral density distribution and various radiographic parameters in patients with advanced medial osteoarthritis of the knee

PURPOSE

Patients with severe osteoarthritis (OA) of the knee have changes in bone mineral density (BMD) of the distal femur and proximal tibia. Correlations between the medial-to-lateral BMD (M/L-BMD) ratio (which normalizes the potentially confounding effects of body size and sex on BMD) and radiographic parameters that indicate OA progression have not been adequately studied. The purpose of this study was to evaluate correlations between radiographic indicators of OA progression and femoral and tibial M/L-BMD ratios.

METHODS

A consecutive series of 182 knees in 156 patients with advanced medial knee OA who underwent total knee arthroplasty were included. We evaluated correlations between the femoral and tibial M/L-BMD ratios and various radiographic parameters, including tibiofemoral angle (TFA), mechanical axis angle (MAA), tibial coronal angle, tibiofemoral subluxation (%), load-bearing axis deviation at the tibial plateau (%), and medial and lateral laxity.

RESULTS

Univariate analyses using Spearman's correlation coefficient revealed significant positive correlations between femoral and tibial M/L-BMD ratios and both TFA and MAA and negative correlations with tibial coronal angle and load-bearing axis deviation. Multivariate analyses showed significant associations between TFA and the femoral M/L-BMD ratio (β = 0.434, p < 0.001) and between MAA and the tibial M/L-BMD ratio (β = 0.384, p < 0.001).

CONCLUSION

BMD distribution around the knee might be predictable with radiographic parameters such as the TFA for the femur and MAA for the tibia. The findings of this study provide in vivo data on the evaluation of preoperative femoral and tibial M/L-BMD ratios without dual-energy X-ray absorptiometry.

Residual medial tightness in extension is corrected spontaneously after total knee arthroplasty in varus knees

PURPOSE

Although soft tissue balancing is considered important for successful total knee arthroplasty (TKA), it is unclear whether the laxity and balance achieved intraoperatively change postoperatively. A recent study demonstrated anaesthesia significantly influenced knee joint laxity after TKA; however, there has been no comparison of the varus-valgus laxity immediately after TKA and in the postoperative period under the same anesthetic conditions. Therefore, quantitative stress arthrometric studies were conducted under identical conditions to identify changes in coronal ligament laxity after TKA spontaneously.

METHODS

A consecutive series of 28 knees with varus of more than 5° in 28 patients undergoing staged bilateral TKAs was prospectively evaluated. Postoperative varus-valgus laxity was measured immediately after surgery, with the patient still under spinal anaesthesia; and again at the time of the contralateral TKA, again under anaesthesia. The mean time between the first and second operations was 9.7 ± 7.3 months.

RESULTS

Mean medial laxity significantly changed from 2.4° ± 1.6° just after the first operation under anaesthesia to 3.8° ± 1.4° just after contralateral TKA under anaesthesia (p < 0.001), but no significant change occurred in lateral laxity (5.6° ± 2.4° just after the first operation and 5.7° ± 2.1° after contralateral TKA, n.s.). Significant negative correlations were identified between laxity immediately after surgery and the amount of laxity change on both the medial (R = - 0.63, p < 0.001) and lateral sides (R = - 0.53, p < 0.001).

CONCLUSION

Spontaneous soft tissue correction occurs after TKA. The findings from this study provides a rationale that it is not necessary for surgeons to perform the medial soft tissue release until the soft tissue tension is equalized on both the medial and lateral sides which has the risk of excessive release leading to instability. In situations where the surgeon is confronted with a knee that becomes too tight or too loose depending on the insert thickness, it is recommended to choose the thicker insert with the understanding that the knee will initially have a slightly tighter medial compartment that will loosen over time. The results of this study provide technical considerations that can help a surgeon achieve adequate postoperative stability.

LEVEL OF EVIDENCE

IV.

Relationship between outcome scores and knee laxity following total knee arthroplasty: a systematic review

Background and purpose - Instability following primary total knee arthroplasty (TKA) is, according to all national registries, one of the major failure mechanisms leading to revision surgery. However, the range of soft-tissue laxity that favors both pain relief and optimal knee function following TKA remains unclear. We reviewed current evidence on the relationship between instrumented knee laxity measured postoperatively and outcome scores following primary TKA. Patients and methods - We conducted a systematic search of PubMed, Embase, and Cochrane databases to identify relevant studies, which were cross-referenced using Web of Science. Results - 14 eligible studies were identified; all were methodologically similar. Both sagittal and coronal laxity measurement were reported; 6 studies reported on measurement in both extension and flexion. In knee extension from 0° to 30° none of 11 studies could establish statistically significant association between laxity and outcome scores. In flexion from 60° to 90° 6 of 9 studies found statistically significant association. Favorable results were reported for posterior cruciate retaining (CR) knees with sagittal laxity between 5 and 10 mm at 75-80° and for knees with medial coronal laxity below 4° in 80-90° of flexion. Interpretation - In order to improve outcome following TKA careful measuring and adjusting of ligament laxity intraoperatively seems important. Future studies using newer outcome scores supplemented by performance-based scores may complement current evidence.

Predictability of open superficial medial collateral ligament lengthening technique in total knee arthroplasty. Comparison of multiple needle puncturing and subperiosteal elevation: A cadaver study

PURPOSE

Lengthening of superficial medial collateral ligament (sMCL) is often needed in total knee replacement for varus osteoarthritis knee. This study aimed to compare the relationship of multiple needle puncturing (MNP) and subperiosteal elevation (SE) for sMCL lengthening on the gap increment and sequential lengthening in cadaveric knees.

HYPOTHESIS

MNP produces more reliable gap increment than SE technique for sMCL lengthening performed in knee flexion.

METHODS

From 8 pairs of cadaveric knees, one knee from each pair was randomly assigned to undergo MNP and the others to SE. In the MNP group, an 18gauge needle was used to puncture through the sMCL, performing five punctures each time of release. For the SE group, a periosteal elevator was used to sequentially deepen distally beneath the sMCL insertion with an increment depth of 5mm each time of release. The primary outcome was the medial gap increment at knee extension and 90° knee flexion after every attempt in each group.

RESULTS

At each level of lengthening, the widening of flexion and extension gap were not significantly different between the two techniques except for lengthening after 4 and 6 attempts of SE that gave greater widening in extension gap. Variability (width of mid 95% of values) was significantly greater for any given number of attempts using SE than MNP (0.5 vs. 0.24mm per attempt for extension and 2.28 vs. 0.95mm per attempt for flexion; both p<0.001).

CONCLUSION

The MNP technique is a reproducible technique for lengthening the sMCL in knee flexion. It has less variability in gap widening compared to the SE technique.

LEVEL OF EVIDENCE

II, controlled randomized laboratory study.