Effect of Medial Soft Tissue Releases During Posterior-Stabilized Total Knee Arthroplasty on Contact Kinematics and Patient-Reported Outcomes

Total Knee Arthroplasty Kinematics Predict Patient-Reported Outcome Measures: Implications for Clinical Kinematic Examinations

BACKGROUND

A core tenet of total knee arthroplasty (TKA) is that achieving more natural kinematics will lead to superior patient outcomes. Yet this relationship has not been proven for large representative cohorts of TKA patients because accurately measuring 3-dimensional TKA kinematics is time-consuming and expensive. But advanced imaging systems and machine learning-enhanced analysis software will soon make it practical to measure knee kinematics preoperatively and postoperatively in the clinic using radiographic methods. The purpose of this study was to assess the reported relationships between TKA kinematics and outcomes and distill those findings into a proposal for a clinically practical protocol for a clinical kinematic exam.

METHODS

This study reviewed the recent literature relating TKA kinematics to patient outcomes. There were 10 studies that reported statistical associations between TKA kinematics and patient outcome scores utilizing a range of functional activities. We stratified these activities by the complexity of the radiographic examination to create a proposed examination protocol, and we generated a list of requirements and characteristics for a practical TKA clinical kinematic examination.

RESULTS

Given considerations for a clinically practical kinematic exam, including equipment, time and other resources, we propose 3 exam levels. With basic radiographs, we suggest studying single-leg stance in extension, lunge or squat, and kneeling. For fluoroscopic systems with X-ray pulses up to 20 ms, we propose chair-rise or stair ascent to provide additional dynamic information. For fluoroscopic systems with X-ray pulses of less than 10 ms, we propose rapid open-chain knee flexion-extension to simulate the highly dynamic swing phase of gait.

CONCLUSIONS

It is our hope that this proposed examination protocol spurs discussion and debate so that there can be a consensus approach to clinical examination of knee and TKA kinematics when the rapidly advancing hardware and software capabilities are in place to do so.

Lateral Subvastus Lateralis versus Medial Parapatellar Approach for Total Knee Arthroplasty: Patient Outcomes and Kinematics Analysis

The conventional approach for total knee arthroplasty (TKA) is a medial parapatellar approach (MPA). We aimed to study patient outcomes and kinematics with a quadriceps sparing lateral subvastus lateralis approach (SLA). Patients with neutral/varus alignment undergoing primary TKA were consented to undergo the SLA. At 1-year postoperative, patients underwent radiostereometric analysis. Patients were administered the Short Form 12 (SF-12), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Knee Society Score (KSS). Kinematics and outcome data were compared to a group undergoing TKA via conventional MPA. Fourteen patients underwent TKA via SLA with a mean age 71.5 ± 8.0 and mean body mass index (BMI) 31.0 ± 4.5. The MPA group had 13 patients with mean age 63.4 ± 5.5 (p = 0.006) and mean BMI 31.2 ± 4.6 (p = 0.95). The SLA resulted in a significantly more posterior medial contact point at 0 (p = 0.011), 20 (p = 0.020), and 40 (p = 0.039) degrees of flexion. There was no significant difference in medial contact point from 60 to 120 degrees, lateral contact point at any degree of flexion, or axial rotation. There was no difference in improvement in postoperative WOMAC, SF-12, KSS function, and total KSS knee scores between groups. The MPA group had a significantly greater improvement in KSS knee scores at 3 months (p < 0.001), 1 year (p = 0.003), and 2 years (p = 0.017). The SLA resulted in increased medial femoral rollback early in flexion. Although both approaches resulted in improved postoperative outcomes, the MPA group showed significantly greater improvements in KSS knee scores at 3 months, 1 year, and 2 years. Further studies are required to identify any benefits that the SLA may offer. LEVEL OF EVIDENCE:  Therapeutic Level II.

Incidence of soft tissue releases in robotic assisted cementless TKA with mechanical alignment and flexion gap balancing

BACKGROUND

To ensure the success of total knee arthroplasty (TKA), precise bone cuts and a well-balanced soft tissue envelope are crucial. Soft tissue release may be necessary, subject to various factors. Therefore, documenting the type, frequency, and necessity of soft tissue releases can establish a benchmark for comparing different alignment techniques and philosophies and evaluating their outcomes. The purpose of this study was to demonstrate that robotic-assisted knee surgery requires minimal soft tissue release.

METHODS

We prospectively documented and retrospectively reviewed the soft tissue releases employed in securing ligament balance in the first 175 patients who received robotic-assisted TKAs at Nepean Hospital. ROSA was utilized in all surgeries with the aim of restoring mechanical coronal alignment, with a flexion gap balancing technique. Surgeries were performed between December 2019 to August 2021 by a single surgeon who used a standard medial parapatellar approach without a tourniquet, and the cementless persona prosthesis. All patients were followed up for a minimum of 6 months post-surgery. Soft tissue releases included any form of medial release for varus knee, posterolateral release for valgus knee and PCL fenestration or sacrifice.

RESULTS

There were 131 female and 44 male patients, aged between 48 to 89 years (average 60 years). The preoperative HKA ranged from 22 degrees varus to 28 degrees valgus, with 71% of patients presenting with a varus deformity. For the whole group, the no need for soft tissue release was documented in 123 patients (70.3%), small fenestrated releases of PCL in 27 (15.4%), sacrifice of PCL in 8 (4.5%), medial releases in 4 (2.3%) and posterolateral releases in 13 (7.4%). In 29.7% of patients in whom a soft tissue release was necessary for balance, over half were/received minor fenestrations of the PCL. Outcomes to date included no revisions or impending revisions, 2 MUAs (1%), and Oxford knee scores averaged 40 at 6 months.

CONCLUSION

We concluded that Robot technology enhanced the precision of bone cuts and allowed for titration of required soft tissue releases to achieve optimal balance.

Correlating Contact Kinematics to Tibial Component Migration Following Cemented Bicruciate Stabilized Total Knee Arthroplasty

BACKGROUND

Contact kinematics in total knee arthroplasty (TKA) has been shown to affect tibial component migration. However, previous studies correlating kinematic variables to implant migration were completed with older TKA designs. The goal of this study was to determine if there are associations between contact kinematics and tibial component migration for a cemented, bicruciate stabilized (BCS) TKA system.

METHODS

A total of 54 knees implanted with a BCS TKA system were analyzed using radiostereometric analysis (RSA). Patients underwent RSA exams at 2 weeks, 6 weeks, 3 months, 6 months, 1 year, and 2 years post operation to measure tibial component migration. At 1 year, contact kinematics was evaluated during a quasi-static deep knee bend. Linear regression analyses were performed between kinematic variables and migration values.

RESULTS

Significant correlations were found between contact kinematics and tibial component migration. Excursion on the lateral condyle was the most consistent variable correlating with implant migration. Six patients had > 0.2 mm migrations from 1 to 2 years post operation indicating continuously migrating tibial components, and most had atypical contact kinematics.

CONCLUSION

Kinematics was shown to influence tibial component migration. Reduced lateral excursion, suggesting a more constrained lateral condyle, resulted in greater implant migration. The 6 patients who had continuously migrating tibial components had demographic factors that may limit the ability to endure unintended force transmissions caused by abnormal kinematics. These results highlight the importance of restoring knee kinematics with this BCS TKA design to minimize improper force transmissions and resultant increased implant migrations.

Patient and Implant Performance of Satisfied and Dissatisfied Total Knee Arthroplasty Patients

BACKGROUND

Implant migration and altered kinematics have been thought to impact patient-reported outcome measures (PROMs) and postoperative patient satisfaction. In this study comparing satisfied and dissatisfied total knee arthroplasty (TKA) patients, we hypothesized that dissatisfied patients will have greater continuous implant migration and that there will be differences in joint kinematics, objective functional measurements, and PROMs between satisfied and dissatisfied patients.

METHODS

The Knee Society Score Satisfaction Subsection questions regarding satisfaction with function were used at least 6 months postoperation to split 50 patients into satisfied and dissatisfied groups. Patients underwent radiostereometric analysis to evaluate migration and kinematics. A wearable sensor system obtained objective measurements of patient function during timed up and go tests. PROMs were recorded preoperation and postoperation.

RESULTS

No statistically significant differences were found in migration between satisfied and dissatisfied groups. Statistical kinematic differences existed in lateral anteroposterior contact location at 20° and 40° of flexion at 1 year, where the dissatisfied group had more anteriorly located lateral contact. No statistically significant differences were present in objective functional measurements. Satisfied and dissatisfied groups had differing PROMs at 4 timepoints or greater for each questionnaire.

CONCLUSIONS

No differences were found in tibial component migration or objectively measured function between satisfied and dissatisfied patients. Functionally dissatisfied patients had more anteriorly positioned contact on the lateral condyle in early flexion and reported more pain and unmet expectations. These findings suggest that improving the functional satisfaction of TKA requires restoration of kinematics in early flexion and management of patient's pain and expectations.

Effect of gap balancing and measured resection techniques on implant migration and contact kinematics of a cementless total knee arthroplasty

BACKGROUND

The purpose of this study was to compare implant migration and tibiofemoral contact kinematics of a cementless primary total knee arthroplasty (TKA) implanted using either a gap balancing (GB) or measured resection (MR) surgical technique.

METHODS

Thirty-nine patients underwent TKA via a GB (n = 19) or a MR (n = 20) surgical technique. Patients received an identical fixed-bearing, cruciate-retaining cementless implant. Patients underwent a baseline radiostereometric analysis (RSA) exam at two weeks post-operation, with follow-up visits at six weeks, three months, six months, and one year post-operation. Migration including maximum total point motion (MTPM) of the femoral and tibial components was calculated over time. At the one year visit patients also underwent a kinematic exam via RSA.

RESULTS

Mean MTPM of the tibial component at one year post-operation was not different (mean difference = 0.09 mm, p = 0.980) between the GB group (0.85 ± 0.37 mm) and the MR group (0.94 ± 0.41 mm). Femoral component MTPM at one year post-operation was also not different (mean difference = 0.27 mm, p = 0.463) between the GB group (0.62 ± 0.34 mm) and the MR group (0.89 ± 0.44 mm). Both groups displayed similar kinematic patterns.

CONCLUSIONS

There was no difference in implant migration and kinematics of a single-radius, cruciate retaining cementless TKA performed using a GB or MR surgical technique. The magnitude of migration suggests there is low risk of early loosening. The results provide support for using the cementless implant with either a GB or MR technique.

Intraoperative physiological lateral laxity in extension and flexion for varus knees did not affect short-term clinical outcomes and patient satisfaction

PURPOSE

Medial release during total knee arthroplasty (TKA) is used to correct ligament imbalance in knees with varus deformity. However, questions remain on whether residual ligament imbalance would be related to inferior clinical results. The purposes of the present study were to measure the intraoperative joint gap and to evaluate the effect of intraoperative soft tissue condition on the new Knee Society Score (KSS 2011) at 2-year follow-up, without the maneuver of additional medial release to correct the asymmetrical gap balance.

METHODS

Varus-valgus gap angle and joint gap were measured using a tensor device without medial release for 100 knees with preoperative varus deformity. The knees were categorized according to the varus-valgus gap angle and the laxity. The preoperative and postoperative clinical outcomes using KSS 2011 were compared between the groups.

RESULTS

The average varus-valgus angles had a residual imbalance of 2.8° varus and 1.3° varus in extension and flexion, respectively. In comparison, according to varus-valgus joint gap angle and knee laxity in extension and flexion, no significant differences were found in postoperative range of motion and subscale of KSS 2011 among the groups.

CONCLUSION

Intraoperative asymmetrical joint gap and physiological laxity do not affect early clinical results after TKA.

LEVEL OF EVIDENCE

III.

Contact kinematics of patient-specific instrumentation versus conventional instrumentation for total knee arthroplasty

BACKGROUND

The goal was to evaluate the joint contact kinematics of total knee arthroplasties implanted using patient-specific instrumentation (PSI) compared to conventional instrumentation (CI). We hypothesized that use of PSI would not significantly alter contact kinematics.

METHODS

The study was a prospective randomized controlled trial, with equal allocation of fifty patients to PSI and CI groups. At two years post-operation, patients underwent weight-bearing stereo X-ray examinations at 0°, 20°, 40°, 60°, 80°, and 100° of flexion. The shortest tibiofemoral distance on each condyle determined the contact location. Magnitude of the shortest distance was measured and condylar separation was analyzed using thresholds of 0.5 and 0.75 mm. Kinematic measurements derived from the shortest distance included anteroposterior (AP) translation, excursion, axial rotation, and paradoxical anterior motion. Pivot position and cam/post contact were also investigated.

RESULTS

There were no differences (p > 0.05) in medial and lateral AP contact locations, excursions, and magnitude of anterior motion, or in axial rotation, pivot patterns, frequency of cam/post engagement, frequency of medial anterior motion, and condylar separation at a 0.75 mm threshold. Significant differences were found in frequency of lateral anterior motion (p = 0.048) and condylar separation at a 0.5 mm threshold (p = 0.010). Both groups displayed typical kinematics for a fixed-bearing posterior-stabilized implant.

CONCLUSIONS

We found no major differences in knee kinematics between PSI and CI groups, which suggest that PSI does not provide a significant kinematic advantage over conventional instruments.

Comparison of Contact Kinematics in Posterior-Stabilized and Cruciate-Retaining Total Knee Arthroplasty at Long-Term Follow-Up

BACKGROUND

There is controversy regarding the superiority of posterior-stabilizing (PS) total knee arthroplasty (TKA) and cruciate-retaining (CR) TKA. Substantial work has made comparisons between PS and CR TKA at follow-ups of less than 5 years. It was the goal of the present study to compare the kinematics at greater than 5 years postoperatively between CR and PS TKA, with a secondary goal of comparing patient function.

METHODS

A total of 42 knees were investigated, with equal representation in the PS and CR TKA groups. Patients underwent radiostereometric analysis imaging at 0°, 20°, 40°, 60° 80°, and 100° of flexion. Contact position, magnitude of excursion, and condylar separation on each condyle were measured. A Timed-Up-and-Go functional test was also performed by patients, with the total test time being measured. Preoperative and postoperative clinical outcome scores were also collected.

RESULTS

There were differences in contact position on both the medial and lateral condyles at multiple angles of flexion (P < .05). There was no difference (P = .89) in medial excursion; however, PS TKA had greater lateral excursion than CR TKA (P < .01). No difference (P > .99) was found in frequency of condylar separation. PS TKA was associated with faster (P = .03) total Timed-Up-and-Go test times. There were no differences in clinical outcome scores between the groups preoperatively or postoperatively.

CONCLUSION

We found kinematic and functional differences that favor PS TKA. Our results suggest posterior cruciate ligament insufficiency in CR TKA, indicating that perhaps the cam/post systems in PS TKA better maintain knee kinematics and function long term.