Lessons learned from selective soft-tissue release for gap balancing in primary total knee arthroplasty: an analysis of 1216 consecutive total knee arthroplasties: AAOS exhibit selection

Investigation of the relationship between soft tissue stiffness and maximum knee extension angle in patients with knee osteoarthritis

Knee extension limitation is a risk factor for knee osteoarthritis (OA) progression. However, the soft tissue stiffness involved in knee extension limitation remains to be determined. This study aimed to clarify the relationship between maximum knee extension angle and tissue stiffness in patients with knee OA using ultrasound shear wave elastography (uSWE). Women aged > 50 years with medial knee OA participated　in this study. We evaluated the maximum knee extension angle in the prone position using a goniometer at 1° increments. The shear wave velocity (SWV) in the prone position at 15° knee flexion of the following tissues was measured using uSWE: medial and lateral posterior capsule, medial collateral ligament, popliteus muscle, biceps femoris short head (middle and distal), and medial and lateral gastrocnemius (middle and proximal). We performed separate simple linear regression analyses with maximum knee extension angle as a dependent variable and the SWV of each tissue as an independent variable. A total of 66 participants were included in this study. The maximum knee extension angle was significantly positively associated with the SWV of medial posterior capsule (β = 0.31, p = 0.012). Conversely, the maximum knee extension angle was negatively associated with the SWV of the proximal medial gastrocnemius (β = -0.35, p < 0.01). There were no associations between other tissues and the maximum knee extension angle. Our results suggest that stiffness of the medial posterior capsule is associated with knee extension limitation in patients with Knee OA.

Robotic-Assisted Primary Total Knee Arthroplasty Requires Fewer Soft-Tissue Releases and Is Associated With a Larger Reduction in Early Postoperative Pain

BACKGROUND

Robotic-assisted total knee arthroplasty (RATKA) has been shown to improve the accuracy of component alignment and to potentially reduce the need for soft-tissue releases. To date, however, the potential benefits of expedited recovery, improved functional outcomes, and improved longevity of RATKA remain unproven. The purpose of this study was to compare functional outcomes and rates of soft-tissue releases between RATKA, conventional instrumentation (CONV), and accelerometer-based navigation (ABN) in primary total knee arthroplasties (TKAs).

METHODS

A retrospective study of 2,338 consecutive TKAs performed by two surgeons was performed. There were 1,216 TKAs performed with CONV and the goal of neutral mechanical alignment. There were 724 TKAs performed with ABN and restricted kinematic alignment goals. There were 398 RATKAs performed with a functional alignment philosophy. Radiographs were reviewed for all knees. We compared Patient-Reported Outcomes Measurement Information System scores (2 weeks, 6 weeks, and 1 year) and rates of soft-tissue releases between ABN and RATKA cohorts. Chi-square tests were used to compare rates of releases between cohorts. Generalized estimating equations were used to evaluate outcomes over time.

RESULTS

Overall, the rate of soft-tissue releases was 47.9% in CONV, 74.4% in the ABN group, and 29.9% in the RATKA group. The RATKAs required significantly fewer medial releases in varus knees than CONV (19.9 versus 46.3%, P < 0.001) and ABN TKAs (19.9 versus 68.8%, P < 0.001). In valgus knees, RATKAs required significantly fewer lateral releases than CONV (33.7 versus 61.6%, P < 0.001) and ABN TKAs (33.7 versus 46.6%, P < 0.001). The RATKA had a greater reduction in pain scores (mean 4.5 more points) than the ABN cohort from preoperative to 6 weeks (P = 0.038) with no difference in pain scores beyond 6 weeks. There were no differences in Patient-Reported Outcomes Measurement Information System scores at 1-year follow-up.

CONCLUSIONS

In this series, RATKA with a functional alignment goal performed by adjusting component placement and bony cuts to balance the knee resulted in fewer soft-tissue releases when compared to conventional instrumented TKA and navigated TKA. The RATKAs also demonstrated a larger reduction in short-term pain scores when compared to ABN TKAs, but no differences in patient-reported outcome scores at 1 year.

Medial Deviation of a 6° Prosthetic Trochlear Groove After Kinematically Aligned Total Knee Arthroplasty Occurs in Four Types of Coronal Plane Alignment of the Knee (CPAK) and Decreases the Forgotten Joint Score

Background

The study focused on kinematically aligned total knee arthroplasty (KA TKA). It identified which coronal plane alignment of the knee (CPAK) types are associated with a higher proportion of medial deviation of the 6° prosthetic trochlear groove (PTG) relative to the quadriceps' line of pull and whether medial deviation adversely affected the Forgotten Joint Score (FJS). The research calculated the minimum PTG angle required to prevent medial deviation by at least 2° in all patients.

Methods

The study analyzed 296 KA TKAs with a postoperative long-leg scanogram and a 2-year FJS score. Radiographic measurements were used to determine the CPAK type and to identify the deviation of the 6° PTG relative to the quadriceps' line of pull as medial (-) or lateral (+).

Results

Fifty-one percent of KA TKAs had a medial deviation of the PTG, and the proportion was higher in CPAK I, II, III, and VI than in IV and V types (P < .05). The median FJS of CPAK III was significantly lower than I and IV (P < .0262) and comparable to II, V, and VI (P > .085). The minimum PTG angle required to prevent medial deviation by at least 2° in all patients is 17°.

Conclusions

A medial deviation of the 6° PTG occurred in more than half of the KA TKAs and was observed in 4 of 6 CPAK types. Because medial deviation was associated with a lower FJS, it is suggested that the femoral component should have a minimum PTG of 17° to prevent medial deviation by at least 2° in all patients.

Level of evidence

IV.

Variability in Alignment and Bone Resections in Robotically Balanced Total Knee Arthroplasties

Image-based robotic-assisted total knee arthroplasty (RA-TKA) allows three-dimensional surgical planning informed by osseous anatomy, with intraoperative adjustment based on a dynamic assessment of ligament laxity and gap balance. The aim of this study was to identify ranges of implant alignment and bone resections with RA-TKA. We retrospectively reviewed 484 primary RA-TKA cases, stratified by preoperative coronal alignment. Demographics and intraoperative data were collected and compared using Chi-square and ANOVA tests. Planned limb, femoral, and tibial alignment became increasingly varus in a progressive order from valgus to neutral to the highest in varus knees (p < 0.001). Planned external transverse rotation relative to the TEA was lowest in the valgus cohort; relative to the PCA, whereas the varus cohort was highest (p < 0.001, both). Planned resections of the lateral distal femur and of the medial posterior femur were greater in the varus group compared to neutral and valgus (p < 0.001). There were significant differences between cohorts in planned tibia resections, laterally and medially. Varus knees demonstrated higher variability, while valgus and neutral had more metrics with low variability. This study demonstrated trends in intraoperative planned alignment and resection metrics across various preoperative coronal knee alignments. These findings contribute to the understanding of RA-TKA and may inform surgical decision-making.

Robotic-assisted total knee arthroplasty reduces soft-tissue releases which improves functional outcomes: A retrospective study

BACKGROUND

There is increasing use of Robotic-Assisted (RA) and personalized alignment techniques in total knee arthroplasty (TKA). The hypothesis of this study was that RA TKA would result in fewer soft-tissue releases, and that fewer soft-tissue releases would be associated with improved clinical outcomes.

METHODS

A retrospective review of an internal company registry was conducted for all primary TKAs performed from Jan 1, 2014, through a database extract date of Nov 4, 2022. These were grouped by whether there was an intentional soft-tissue release performed (STR) during the surgery or not (NSTR) and whether RA was utilized. The incidence of STR was compared between RA-TKAs and those performed with manual instrumentation. Knee Society Score (KSS) and Knee Society Function Scores (KSFS) were collected at 6 months, 1 year and 2 years. Kaplan-Meier survivorship was performed.

RESULTS

The incidence of STR was significantly lower for RA vs. Manual (43.81% Vs 86.62%, p < 0.0001). The TKAs with NSTR had higher KSFS compared to those with STR at 6 months (84.73 Vs. 77.51, p < 0.0001), 1 year (89.87 Vs. 83.54, p < 0.0001) and 2 years (90.09 Vs. 82.65, p < 0.0001). There was no difference in survivorship, or KSS at any time point. However, the NSTR group had improved KSS pain sub score at 2 years.

CONCLUSION

The results of this observational, retrospective analysis found that the incidence of soft-tissue release was lower with RA-TKA. Further, regardless of if RA was used, avoiding releases was associated with improved KSFS and KSS pain scores through 2 years post-operatively.

Phenotype-considered kinematically aligned total knee arthroplasty for windswept-deformity-associated osteoarthritis: surgical strategy and clinical outcomes

BACKGROUND

Windswept deformity (WSD) in relation to advanced osteoarthritis (OA) presents a significant surgical challenge in total knee arthroplasty (TKA). The primary goal of this study is to investigate the Prevalance of WSD associated osteoarthritis who have undergone total knee arthroplasty. The secondary goal is to explore the causes of WSD and its association with spinal deformity or leg length discrepancy in these patients. Finally, we evaluate the surgical outcomes of phenotype-considered kinematically aligned TKA (KA-TKA) in treating patients with WSD.

METHODS

A review was conducted on data from 40 knees of 33 WSD patients who underwent phenotype-considered KA-TKA from August 2016 to December 2020. Patient demographics, associated diseases, preoperative and postoperative knee alignment angles, range of motion (ROM), Oxford Knee Score (OKS), and Knee Society Score (KSS) were collected and analyzed. Subgroup analysis for comparing the results between valgus and varus knees were also performed.

RESULTS

Within the studied cohort of WSD patients, a substantial 64% displayed concomitant coronal spinal imbalance and 21% evidenced leg length discrepancy. Postoperative improvements were notable in knee alignments, ROM, OKS, and KSS following the application of the phenotype-considered KA-TKA approach. There were significant differences in the knee alignment angles, including mHKA, LDFA, and MPTA, between the valgus and varus side of knees (P = 0.018). However, no statistically significant difference were observed in the functional scores, comprising ROM, OKS, and KSS, between valgus and varus knees.

CONCLUSIONS

A high percentage of patients with WSD exhibited coronal spinal imbalance and leg length discrepancy. Phenotype-considered KA-TKA effectively provided alignment targets for the treatment of both varus and valgus knees in patients with WSD, achieving excellent short-term outcomes and acceptable knee alignment.

Increase in the Posterior Tibial Slope Provides Better Joint Awareness and Patient Satisfaction in Cruciate-Retaining Total Knee Arthroplasty

The effect of the posterior tibial slope (PTS) in cruciate-retaining total knee arthroplasty (CR-TKA) on clinical outcomes remains unclear. We aimed to investigate (1) the effect of alteration of the PTS on clinical outcomes, including patient satisfaction and joint awareness, and (2) the relationship between the patient-reported outcomes, the PTS, and compartment loading. Based on the alteration of the PTS after CR-TKA, 39 and 16 patients were stratified into increased and decreased PTS groups, respectively. Clinical evaluation was performed by the Knee Society Score (KSS) 2011 and the Forgotten Joint Score-12 (FJS-12). Compartment loading was intraoperatively assessed. KSS 2011 (symptoms, satisfaction, and total score) was significantly higher (p = 0.018, 0.023, and 0.040, respectively), and FJS ("climbing stairs?") was significantly lower (p = 0.025) in the increased PTS group compared with the decreased PTS group. The decrease in both medial and lateral compartment loading of Δ45°, Δ90°, and ΔFull was significantly greater in the increased PTS group than in the decreased PTS group (p< 0.01 for both comparisons). Medial compartment loading of Δ45°, Δ90°, and ΔFull significantly correlated with KSS 2011 for "symptom" (r = - 0.4042, -0.4164, and -0.4010, respectively; p = 0.0267, 0.0246, and 0.0311, respectively). ΔPTS significantly correlated with medial compartment loading differentials of Δ45°, Δ90°, and ΔFull (r = - 0.3288, -0.3792, and -0.4424, respectively; p = 0.0358, 0.01558, and 0.0043, respectively). Patients with increased PTS showed better symptoms and higher patient satisfaction compared with those with decreased PTS following CR-TKA, possibly due to a greater decrease in compartment loading during knee flexion.Level of evidence:level IV, therapeutic case series.

Complete Release of the Superficial Medial Collateral Ligament in Total Knee Arthroplasty

Background

Proper soft-tissue balance was essential in total knee arthroplasty (TKA). Superficial medial collateral ligament (sMCL) release has been recommended in correction of severe varus knee. However, it has concerns of overcorrection. This study aimed to analyze coronal plane laxity in sMCL-released TKA patients.

Methods

We prospectively collected data from TKA patients who were operated from January 2015 to November 2018. All patients went through the same surgical steps; however, sMCL was left intact in mild-to-moderate deformity (sMCL-intact), while it was completely released in patients with severe deformity (sMCL-released). All patients went through the same postoperative protocol. We used stress radiograph with 90 N force to evaluate coronal plane laxity and recorded modified Western Ontario and McMaster Universities Osteoarthritis Index score at 3- to 6-year postoperative appointments.

Results

There were 46 patients (59 knees) included with an average follow-up time of 48.3 months. The sMCL-intact group consisted of 14 patients (16 knees) with average preoperative mechanical axis (MA) varus of 4.84 degrees exhibited 1.64 mm (0.6-3.6 mm) laxity on medial side and 1.01 mm (0-3.1 mm) on lateral side. The sMCL-released group consisted of 32 patients (43 knees) with average preoperative MA varus of 14.74 degree exhibited 1.96 mm (0.4-4.8 mm) laxity on medial side and 1.57 mm (0.1-5.9 mm) on lateral side. At the time of follow-up, the mean modified Western Ontario and McMaster Universities Osteoarthritis Index in the sMCL-intact and sMCL-released groups were 14.8 and 13.5 (P value .79), respectively. There was no clinical laxity or reoperation of any causes in either groups.

Conclusions

Complete release of sMCL in severe varus knee does not result in overcorrection after TKA at the midterm follow-up period. Thus, sMCL release technique could be an effective and safe option for correction of severe varus deformity.

Demonstration of the Medial Subvastus Knee Exposure for MACI Implantation

Background

There are several techniques for knee exposure in treating chondral defects with restorative procedures. The medial subvastus knee exposure is often overlooked when choosing the surgical approach. When properly performed, the medial subvastus approach can allow for the treatment of a wide range of pathology while preserving the extensor mechanism.

Indications

We present a case of an active 40-year-old man with persistent left knee pain noted to have a full-thickness medial femoral condylar articular cartilage defect in an otherwise healthy appearing knee.

Technique Description

The rationale and considerations for the medial subvastus knee exposure in treating a chondral defect with an autologous chondrocyte implant are discussed. Careful consideration of the approach, intra-articular exposure, and closure are emphasized to achieve optimal outcomes.

Results

At 18 months postoperative, the patient reported no knee pain with improvements made in Knee injury and Osteoarthritis Outcome Score (KOOS), Lysholm, and International Knee Documentation Committee (IKDC) scores. These results are consistent with our institutions larger cohort of 26 patients undergoing matrix-induced autologous chondrocyte implantation (MACI) using the subvastus approach. These improvements in patient-reported outcomes are maintained at 2 years postoperative and are consistent with other published outcomes of the MACI procedure.

Discussion/Conclusion

Excellent results in addressing chondral pathology about the knee can be achieved by selecting the appropriate surgical access. The subvastus approach has several advantages such as preserving the quadriceps mechanism, improving postoperative quadriceps muscle strength, conservation of the patellar genicular blood supply and possibly reducing postoperative pain that can result in a faster rehabilitation. When performed systematically and carefully, complete exposure of the knee can be achieved to facilitate a wide variety of surgical interventions. In patients undergoing cartilage restoration procedures, the medial subvastus approach should be considered in the surgeon's armamentarium.

Patient Consent Disclosure Statement

The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Shear wave tensiometry tracks reductions in collateral ligament tension due to incremental releases

Surgeons routinely perform incremental releases on overly tight ligaments during total knee arthroplasty (TKA) to reduce ligament tension and achieve their desired implant alignment. However, current methods to assess whether the surgeon achieved their desired reduction in the tension of a released ligament are subjective and/or do not provide a quantitative metric of tension in an individual ligament. Accordingly, the purpose of this study was to determine whether shear wave tensiometry, a novel method to assess tension in individual ligaments based on the speed of shear wave propagation, can detect changes in ligament tension following incremental releases. In seven medial and eight lateral collateral porcine ligaments (MCL and LCL, respectively), we measured shear wave speeds and ligament tensions before and after incremental releases consisting of punctures with an 18-gauge needle. We found that shear wave speed squared decreased linearly with decreasing tension in both the MCL (average coefficient of determination (R2 avg ) = 0.76) and LCL (R2 avg  = 0.94). We determined that errors in predicting tension following incremental releases were 26.2 and 14.2 N in the MCL and LCL, respectively, using ligament-specific calibrations. These results suggest shear wave tensiometry is a promising method to objectively measure the tension reduction in released structures. Clinical Significance: Direct, objective measurements of the tension changes in individual ligaments following release could enhance surgical precision during soft tissue balancing in total knee arthroplasty. Thus, shear wave tensiometry could help surgeons reduce the risk of poor outcomes associated with overly tight ligaments, including residual knee pain and stiffness.

Moving beyond radiographic alignment: applying the Wald Principles in the adoption of robotic total knee arthroplasty

The use of robotics in total knee arthroplasty (TKA) is growing at an exponential rate. Despite the improved accuracy and reproducibility of robotic-assisted TKA, consistent clinical benefits have yet to be determined, with most studies showing comparable functional outcomes and survivorship between robotic and conventional techniques. Given the success and durability of conventional TKA, measurable improvements in these outcomes with robotic assistance may be difficult to prove. Efforts to optimize component alignment within two degrees of neutral may be an attainable but misguided goal. Applying the "Wald Principles" of rationalization, it is possible that robotic technology may still prove beneficial, even when equivalent clinical outcomes as conventional methods, if we look beyond the obvious surrogate measures of success. Robotic systems may help to reduce inventory, streamline surgical trays, enhance workflows and surgical efficiency, optimize soft tissue balancing, improve surgeon ergonomics, and integrate artificial intelligence and machine learning algorithms into a broader digital ecosystem. This article explores these less obvious alternative benefits of robotic surgery in the field of TKA.

Restricted Inverse Kinematic Alignment Better Restores the Native Joint Line Orientation While Achieving Similar Balance, Laxity, and Arithmetic Hip-Knee-Ankle Angle to Gap Balancing Total Knee Arthroplasty

Background

Both restricted inverse kinematic alignment (iKA) and gap balancing aim for a balanced total knee arthroplasty by adjusting femoral component position based on ligamentous gaps. However, iKA targets a native tibial joint line vs resecting perpendicular to the mechanical axis. This study compares how these 2 techniques impact the balance and laxity throughout flexion and joint line obliquity (JLO), arithmetic hip-knee-ankle angle (aHKA), and the coronal plane alignment of the knee (CPAK).

Methods

Two surgeons performed 75 robot-assisted iKA total knee arthroplasties. A digital joint tensioner collected laxity data throughout flexion before femoral resection. The femoral component position was determined using predictive gap-planning to optimize the balance throughout flexion. Planned gap balancing (pGB) simulations were performed for each case using neutral tibial resections. Mediolateral balance, laxity, and CPAK were compared among pGB, planned iKA (piKA), and final iKA.

Results

Both piKA and pGB had similar mediolateral balance and laxity, with mean differences <0.4 mm. piKA had a lower mean absolute difference from native JLO than pGB (3 ± 2° vs 7 ± 4°, P < .001). aHKA was similar (P > .05) between pGB and piKA. piKA recreated a more native CPAK distribution, with types I-V being the most common ones, while most pGB knees were of type V, VII, and III. Final iKA and piKA had similar mediolateral balance and laxity, with a root-mean-square error <1.4 mm.

Conclusions

Although balance, laxity, and aHKA were similar between piKA and pGB, piKA better restored native JLO and CPAK phenotypes. The neutral tibial resection moved most pGB knees into types V, VII, and III. Surgeons should appreciate how the alignment strategy affects knee phenotypes.

Bilateral Knee Arthroplasty in Patients Affected by Windswept Deformity: A Systematic Review

Background: “Windswept” deformity (WSD) consists of a non-frequent condition in which the patient presents a valgus deformity in one knee and a varus deformity in the other. We performed a review of the available literature to aggregate the accessible data on the outcomes of bilateral knee arthroplasty in patients with WSD and to discuss the surgical challenges that this condition might pose. Methods: A systematic review of the literature following the PRISMA guidelines was conducted. The relevant studies between 1979 and 2021 were identified. Four studies with a total of 68 patients were included for analysis. The mean follow-up for varus knees was 3.3 years, 3.1 years for valgus knees. The quality and rigor of the included studies was assessed using the Methodological index for non-randomized studies (MINORS). Results: All the studies reported improvement in knee function following knee replacement surgery, and a reduction in axial deviation of both knees, with similar results in valgus and varus knees in terms of patient satisfaction. The most relevant data were that unicompartmental knee arthroplasty (UKA) allowed for limited axial correction with slightly inferior functional results. Kinematic alignment (KA) allowed for similar results in both knees. Conclusion: The present review shows how satisfactory results can be achieved in both knees in patients with WSD and osteoarthrosis (OA). However, the operating surgeon should be aware of the importance of the implant choice in terms of functional outcomes. In the absence of extra-articular deformities, calipered KA total knee arthroplasty (TKA) can be performed on both knees with good axial correction and functional outcome. Level of evidence: II —Systematic review of cohort studies.

Inflammatory Response in Robotic-Arm-Assisted Versus Conventional Jig-Based TKA and the Correlation with Early Functional Outcomes: Results of a Prospective Randomized Controlled Trial

BACKGROUND

Although the exact etiology of patient dissatisfaction in total knee arthroplasty (TKA) is unclear, the inflammatory response precipitated by surgery may be implicated. Robotic TKA has been shown to result in reduced bone and soft-tissue trauma. The objectives of this study were to compare the inflammatory response in conventional jig-based TKA versus robotic-arm-assisted TKA and to examine the relationship with early functional outcomes.

METHODS

This prospective randomized controlled trial included 15 patients with symptomatic knee osteoarthritis undergoing conventional TKA and 15 undergoing robotic-arm-assisted TKA. Blood samples were collected for up to 28 days postoperatively, and predefined markers of systemic inflammation were measured in serum. The local inflammatory response was assessed by analyzing samples from the intra-articular drain fluid at 6 and 24 hours. Relationships with early functional outcomes were evaluated using the Spearman rank correlation coefficient.

RESULTS

Patients in the robotic TKA group demonstrated lower levels of interleukin (IL)-6 in the drain fluid at 6 hours (798.54 pg/mL versus 5,699.2 pg/mL, p = 0.026) and 24 hours and IL-8 at 6 hours. Robotic TKA was associated with lower pain scores on postoperative days 1, 2, and 7. Patient-reported outcome measures were comparable between the 2 groups at 2 years. Significant correlations were observed between all serum markers except IL-1b and self-reported pain on postoperative day 7; between drain IL-8 levels and pain on postoperative days 1 (r = 0.458), 2, and 7; and between drain IL-6, IL-8, and tumor necrosis factor-alpha levels at 6 hours and knee flexion or extension.

CONCLUSIONS

Robotic-arm-assisted TKA was associated with a reduction in the early postoperative local inflammatory response. We also found a moderate relationship between the inflammatory responses and self-reported pain, knee flexion, and knee extension. Further validation of these findings on a larger scale and using longer-term outcomes will be key to developing the optimal TKA procedure.

LEVEL OF EVIDENCE

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

Mechanical Alignment in Knee Replacement Homogenizes Postoperative Coronal Hip-Knee-Ankle Angle in Varus Knees: A Navigation-Based Study

After knee replacement, postoperative lower limb alignment is influenced by the geometry of the prosthesis position and surrounding soft tissue that contributes to the hip-knee-ankle (HKA) angle. The purpose of this study is to determine the dynamic coronal HKA angle after mechanical alignment in total knee replacement using computer navigation. We conducted a pre-post design study of 71 patients with varus osteoarthritic knees on which total knee arthroplasty was performed. The HKA was measured before and at the end of the surgical procedure with the patient in the supine position using a navigation system at 30, 60, and 90 degrees of knee flexion. Postoperative implant position and flexion and extension gaps were assessed. HKA was clustered in three preoperative dynamic patterns (PDPs; Varus-Neutral, Varus-Valgus, and Varus-Varus). There were statistically significant differences in the dynamic coronal HKA between the preoperative and postoperative statuses after mechanically aligned knee replacement (with p < 0.0001) Before the surgical procedure, statistically significant differences were found between patterns at any angle of flexion confirming a well-differentiated preoperative dynamic behavior between the three groups. Postoperatively, 98.6% (71 out of 72) of the knees were within ± 3 degrees of the HKA at full extension. Fifty-eight knees (80.6%) were assessed to a "within-range" postoperative dynamic alignment at any grade of flexion considered. There are differences between the preoperative and postoperative status of the dynamic coronal HKA angle after mechanically aligned knee replacement. We proposed that an excellent dynamic HKA alignment is achieved not only at full extension within the range of 0 ± 3 degrees but also when this alignment is maintained at 30, 60, and 90 degrees.

Impact of Component Alignment and Soft Tissue Release on 2-Year Outcomes in Total Knee Arthroplasty

BACKGROUND

The objective of this study was to investigate the impact of alignment and soft tissue release on patient outcomes following total knee arthroplasty (TKA).

METHODS

In a multicenter study, soft tissue releases during TKA were prospectively documented in 330 robotic-assisted TKAs. Knee Injury and Osteoarthritis Outcome Scores (KOOS) were captured postoperatively. Delphi analysis was used to determine inlier and outlier component alignment boundaries: Tibia Coronal (TC): ±3°, Femur Coronal (FC): ±3°, Femoral Axial (FA): 3°Int-6°Ext, Hip-Knee-Ankle (HKA): 3°Val-4°Var, and Tibiofemoral Axial (TFA): 3°Int-6°Ext. Kruskal-Wallis analysis of variance tests were used to compare groups.

RESULTS

No significant differences were found between any individual or grouped inlier and outlier alignment criterion and KOOS at any timepoint. Outlier alignment frequencies were: TC: 0%, FC: 12%, FA: 8%, HKA: 9%, TFA: 8%, and Any: 23%. Soft tissue releases were performed in 18% of cases. Knees with soft tissue releases reported significantly worse KOOS scores at: 6M: Symptoms (80.0 versus 75.3, P = .03), activities of daily living (ADL) (86.2 versus 80.8, P = .030), quality of life (70.1 versus 60.9, P = .008), 12M ADL (90.0 versus 85.1, P = .023), and 24M ADL (91.9 versus 87.2, P = .016). A higher proportion of patients achieved Minimal Clinically Important Difference for pain at 6 months for those having no releases versus released (92.3% versus 81.0%, P = .021). No significant associations were found between preoperative deformity and preoperative or postoperative KOOS.

CONCLUSION

The addition of soft tissue releases after bony cuts is associated with worse KOOS scores out to 2 years and was more prevalent in knees with worse deformity, while no such association was found for alignment.

Predictive Gap-balancing Reduces the Extent of Soft-tissue Adjustment Required After Bony Resection in Robot-assisted Total Knee Arthroplasty-A Comparison With Simulated Measured Resection

Background

To understand the extent and frequency of soft-tissue adjustment required to achieve mediolateral (ML) balance in measured resection (MR) vs gap-balancing (GB) total knee arthroplasty, this study compared ML balance and joint laxity throughout flexion between the 2 techniques. The precision of predictive GB in achieving ML balance and laxity was also assessed.

Methods

Two surgeons performed 95 robot-assisted GB total knee arthroplasties with predictive balancing, limiting tibial varus to 3° and adjusting femoral positioning to optimize balance. A robotic ligament tensioner measured joint laxity. Planned MR (pMR) was simulated by applying neutral tibial and femoral coronal resections and 3° of external femoral rotation. ML balance, laxity, component alignment, and resection depths were compared between planned GB (pGB) and pMR. ML balance and laxity were compared between pGB and final GB (fGB).

Results

The proportion of knees with >2 mm of ML imbalance in flexion or extension ranged from 3% to 18% for pGB vs 50% to 53% for pMR (P < .001). Rates of ML imbalance >3 mm ranged from 0% to 9% for pGB and 30% to 38% for MR (P < .001). The mean pMR laxity was 1.9 mm tighter medially and 1.1 mm tighter laterally than pGB throughout flexion. The mean fGB laxity was greater than the mean pGB laxity by 0.5 mm medially and 1.2 mm laterally (P < .001).

Conclusion

MR led to tighter joints than GB, with ML gap imbalances >3 mm in 30% of knees. GB planning improved ML balance throughout flexion but increased femoral posterior rotation variability and bone resection compared to MR. fGB laxity was likely not clinically significantly different than pGB.

Influence of Patella Position on Soft Tissue Balance and Clinical Outcomes in Patients Undergoing Minimally Invasive Total Knee Arthroplasty, a Randomized Clinical Trial

Background

We hypothesized that subluxating patellar during minimally invasive total knee arthroplasty (MIS-TKA) would affect intraoperative soft tissue balance and postoperative clinical outcome.

Methods

From December 2018 to May 2020, 189 patients receiving primary MIS-TKA were enrolled. The gap-balance technique was used, with patients randomly assigned to undergo osteotomy and balance of soft tissue with patella reduced (group A; n = 93) or subluxated (group B; n = 96). The gap and varus?valgus angle were compared between groups in both extension and flexion position. The gap and varus?valgus angle were also compared before and after reducing patellar in group B. Femoral prosthesis rotation, mechanical femoral axis–to–tibial axis angle, Knee Society Score (KSS), visual analog scale (VAS), and range of motion (ROM) were compared postoperatively between two groups. Follow-up was 12 months.

Results

The flexion gap and the varus angle were significantly greater (0.4 mm and 0.7 degree) after patella reduction than before reduction, but the extension joint gap and varus angle were comparable before and after patella reduction. The femoral prosthesis tended to be internally rotated (0.65 degree) in group B. ROM and VAS was better in the group A than in group B at 1 month after surgery, but the differences were not significant at 3, 6 and 12 months. KSS was comparable between the groups after surgery.

Conclusions

During MIS-TKA, as far as possible, soft tissue balance should be achieved with the patella reduced; otherwise, the femoral prosthesis may be installed more internally and, after patella reduction, the flexion gap and varus angle would increase.

Clinical Trial Registration

Current Controlled Trials ChiCTR2000034106, https://www.chictr.org.cn/hvshowproject.aspx?id=39987.

Adjusting Insert Thickness and Tibial Slope Do Not Correct Internal Tibial Rotation Loss Caused by PCL Resection: In Vitro Study of a Medial Constraint TKA Implanted with Unrestricted Calipered Kinematic Alignment

Most medial stabilized (MS) total knee arthroplasty (TKA) implants recommend excision of the posterior cruciate ligament (PCL), which eliminates the ligament's tension effect on the tibia that drives tibial rotation and compromises passive internal tibial rotation in flexion. Whether increasing the insert thickness and reducing the posterior tibial slope corrects the loss of rotation without extension loss and undesirable anterior lift-off of the insert is unknown. In 10 fresh-frozen cadaveric knees, an MS design with a medial ball-in-socket (i.e., spherical joint) and lateral flat insert was implanted with unrestricted calipered kinematic alignment (KA) and PCL retention. Trial inserts with goniometric markings measured the internal-external orientation relative to the femoral component's medial condyle at maximum extension and 90 degrees of flexion. After PCL excision, these measurements were repeated with the same insert, a 1 mm thicker insert, and a 2- and 4-mm shim under the posterior tibial baseplate to reduce the tibial slope. Internal tibial rotation from maximum extension and 90 degrees of flexion was 15 degrees with PCL retention and 7 degrees with PCL excision (p < 0.000). With a 1 mm thicker insert, internal rotation was 8 degrees (p < 0.000), and four TKAs lost extension. With a 2 mm shim, internal rotation was 9 degrees (p = 0.001) and two TKAs lost extension. With a 4 mm shim, internal rotation was 10 degrees (p = 0.002) and five TKAs lost extension and three had anterior lift-off. The methods of inserting a 1 mm thicker insert and reducing the posterior slope did not correct the loss of internal tibial rotation after PCL excision and caused extension loss and anterior lift-off in several knees. PCL retention should be considered when using unrestricted calipered KA and implanting a medial ball-in-socket and lateral flat insert TKA design, so the progression of internal tibial rotation and coupled reduction in Q-angle throughout flexion matches the native knee, optimizing the retinacular ligaments' tension and patellofemoral tracking.

Improved femoral component rotation in total knee arthroplasty: an anatomical study with optimized gap balancing

INTRODUCTION

Surgically balanced total knee arthroplasties have shown improved functional and clinical outcomes. Two different alignment methods have been proposed, the measured resection technique which uses femoral landmarks on the one hand and the ligament balanced technique which uses spreaders on the other. As anatomical landmarks also vary widely, with regards to the tibial cut irrespective of the collateral ligaments, we hypothesized that anatomical landmarks are not suitable for ideal femoral component rotational alignment.

MATERIALS AND METHODS

Ten cadaveric bilateral knees underwent TKA using a navigational device and a double tensiometer. By means of the navigational device, flexion gaps were balanced by femoral component size, rotation and flexion until a symmetric flexion and extension gap was obtained. Acquired femoral component rotation was compared to femoral landmarks (Whiteside Line, posterior condylar line and trans-epicondylar line).

RESULTS

Using the Whiteside line, the posterior condylar line and the surgical trans-epicondylar line to identify femoral component rotation did not balance the flexion gap as well as navigation. Depending on the parameter, deviations in femoral rotation of up to 6° were observed compared to the gap balancing technique. Furthermore, large deviations between these landmarks were observed.

CONCLUSION

Based on this study flexion gap balancing can be better optimized using ligament balancing technique. As this technique is highly dependent on the proximal tibial cut, we do recommend the use of navigational devices, which additionally assure a neutral leg alignment.

Postoperative laxity of the lateral soft tissue is largely negligible in total knee arthroplasty for varus osteoarthritis

PURPOSE

To evaluate the integrity of lateral soft tissue in varus osteoarthritis knee by comparing the mechanical axis under varus stress during navigation-assisted total knee arthroplasty before and after compensating for a bone defect with the implant.

METHODS

Sixty-six knees that underwent total knee arthroplasty were investigated. The mechanical axis of the operated knee was evaluated under manual varus stress immediately after knee exposure and after navigation-assisted implantation. The correlation between each value of the mechanical axis and degree of preoperative varus deformity was compared by regression analysis.

RESULTS

The maximum mechanical axis under varus stress immediately after knee exposure increased in proportion to the degree of preoperative varus deformity. Moreover, the maximum mechanical axis under varus stress after implantation increased in proportion to the degree of preoperative varus deformity. Therefore, the severity of varus knee deformity leads to a progressive laxity of the lateral soft tissue. However, regression coefficients after implantation were much smaller than those measured immediately after knee exposure (0.99 vs 0.20). Based on the results of the regression formula, the postoperative laxity of the lateral soft tissue was negligible, provided that an appropriate thickness of the implant was compensated for the bone and cartilage defect in the medial compartment without changing the joint line.

CONCLUSION

The severity of varus knee deformity leads to a progressive laxity of the lateral soft tissue. However, even if the degree of preoperative varus deformity is severe, most cases may not require additional procedures to address the residual lateral laxity.

Restoring the Patient's Pre-Arthritic Posterior Slope Is the Correct Target for Maximizing Internal Tibial Rotation When Implanting a PCL Retaining TKA with Calipered Kinematic Alignment

INTRODUCTION

The calipered kinematically-aligned (KA) total knee arthroplasty (TKA) strives to restore the patient's individual pre-arthritic (i.e., native) posterior tibial slope when retaining the posterior cruciate ligament (PCL). Deviations from the patient's individual pre-arthritic posterior slope tighten and slacken the PCL in flexion that drives tibial rotation, and such a change might compromise passive internal tibial rotation and coupled patellofemoral kinematics.

METHODS

Twenty-one patients were treated with a calipered KA TKA and a PCL retaining implant with a medial ball-in-socket and a lateral flat articular insert conformity that mimics the native (i.e., healthy) knee. The slope of the tibial resection was set parallel to the medial joint line by adjusting the plane of an angel wing inserted in the tibial guide. Three trial inserts that matched and deviated 2°> and 2°< from the patient's pre-arthritic slope were 3D printed with goniometric markings. The goniometer measured the orientation of the tibia (i.e., trial insert) relative to the femoral component.

RESULTS

There was no difference between the radiographic preoperative and postoperative tibial slope (0.7 ± 3.2°, NS). From extension to 90° flexion, the mean passive internal tibial rotation with the pre-arthritic slope insert of 19° was greater than the 15° for the 2°> slope (p < 0.000), and 15° for the 2°< slope (p < 0.000).

DISCUSSION

When performing a calipered KA TKA with PCL retention, the correct target for setting the tibial component is the patient's individual pre-arthritic slope within a tolerance of ±2°, as this target resulted in a 15-19° range of internal tibial rotation that is comparable to the 15-18° range reported for the native knee from extension to 90° flexion.

Total knee arthroplasty in valgus knee deformity: is it still a challenge in 2021?

Total knee arthroplasty in valgus knee deformities continues to be a challenge for a surgeon. Approximately 10% of patients who undergo total knee arthroplasty have a valgus deformity. While performing total knee arthroplasty in a severe valgus knee, one should aware with the technical aspects of surgical exposure, bone cuts of the distal femur and proximal tibia, medial and lateral ligament balancing, flexion and extension gap balancing, creating an appropriate tibiofemoral joint line, balancing the patellofemoral joint, preserving peroneal nerve function, and selection of the implant regarding constraint. Restoration of neutral mechanical axis and correct ligament balance are important factors for stability and longevity of the prosthesis and for good functional outcome. Thus, our review aims to provide step by step comprehensive knowledge about different surgical techniques for the correction of severe valgus deformity in total knee arthroplasty.

Higher revision rate for posterior cruciate-retaining than posterior-stabilized total knee arthroplasty for the treatment of valgus osteoarthritis

PURPOSE

Determining the point at which a valgus deformity requires a more invasive therapy-in this case PS TKA-is surgically challenging. Retaining the posterior cruciate ligament has both advantages and disadvantages. The aim was to evaluate the failure rate and clinical outcomes.

METHODS

248 patients with valgus gonarthrosis underwent surgical treatment: 167 CR TKA cases and 81 PS TKA cases. The KOOS and the OKS were recorded, and 201 patients (133 CR, 68 PS) were recruited into the retrospective study. The influence of BMI and degree of preoperative valgus deformity on the clinical outcome was determined. The revision rate was documented and analysed.

RESULTS

Of 201 patients, 10 required revision surgery owing to instability (10/133 CR, 0/68 PS). Based on the KOOS and the OKS, no significant difference between CR TKA and PS TKA was found. BMI and degree of valgus deformity had no effect on the clinical outcome.

CONCLUSIONS

No difference in the clinical outcome between the CR and PS TKA patients was found. In the CR group, significantly more patients showed 'excellent' OKS than in the PS group. However, 8.0% of the patients in the CR group and none in the PS group underwent surgery due to instability. A higher rate of dissatisfied patients in the CR group is likely. In our clinic, we no longer perform CR TKA for valgus cases.

A cruciate-retaining implant can treat both knees of most windswept deformities when performed with calipered kinematically aligned TKA

PURPOSE

Surgeons performing total knee arthroplasty (TKA) on the osteoarthritic valgus deformity often use a posterior stabilized (PS) and semi-constrained implants to substitute for the release of a contracted posterior cruciate ligament (PCL) instead of a cruciate retaining (CR) implant. Calipered kinematic alignment (KA) strives to retain the PCL and use a CR implant. The aim of this study of the windswept deformity was to determine whether the level of implant constraint, outcome scores, and alignment after bilateral calipered KA TKA are different between a pair of knees with a varus and valgus deformity in the same patient.

METHODS

A review of a prospectively collected database identified all patients with a windswept deformity treated with bilateral TKA (n = 19) out of 2430 consecutive primary TKAs performed between 2014 and 2019. Operative reports determined the level of implant constraint. Patient response to the Forgotten Joint Score (FJS) and Oxford Knee Score (OKS) assessed outcomes at a mean follow-up of 2.3 years. Postoperative alignment was measured on an A-P computer tomographic scanogram of the limb.

RESULTS

CR implants were used in 15 of 19 (79%) valgus deformities and 17 of 19 (89%) of varus deformities (n.s.). No knees required a semi-constrained implant. There was no difference in the median postoperative FJS and OKS (n.s.), and a 1° or less difference in the mean postoperative distal lateral femoral angle (p = 0.005) and proximal medial tibial angle (n.s.) between the paired varus and valgus knee deformity.

CONCLUSION

Based on this small series, surgeons that use calipered KA TKA can expect to use CR implants in most patients with windswept deformity and achieve comparable outcome scores and alignment between the paired varus and valgus deformity.

LEVEL OF EVIDENCE

IV.

A prospective randomized controlled trial comparing the systemic inflammatory response in conventional jig-based total knee arthroplasty versus robotic-arm assisted total knee arthroplasty

AIMS

The primary aim of this study was to compare the postoperative systemic inflammatory response in conventional jig-based total knee arthroplasty (conventional TKA) versus robotic-arm assisted total knee arthroplasty (robotic TKA). Secondary aims were to compare the macroscopic soft tissue injury, femoral and tibial bone trauma, localized thermal response, and the accuracy of component positioning between the two treatment groups.

METHODS

This prospective randomized controlled trial included 30 patients with osteoarthritis of the knee undergoing conventional TKA versus robotic TKA. Predefined serum markers of inflammation and localized knee temperature were collected preoperatively and postoperatively at six hours, day 1, day 2, day 7, and day 28 following TKA. Blinded observers used the Macroscopic Soft Tissue Injury (MASTI) classification system to grade intraoperative periarticular soft tissue injury and bone trauma. Plain radiographs were used to assess the accuracy of achieving the planned postioning of the components in both groups.

RESULTS

Patients undergoing conventional TKA and robotic TKA had comparable changes in the postoperative systemic inflammatory and localized thermal response at six hours, day 1, day 2, and day 28 after surgery. Robotic TKA had significantly reduced levels of interleukin-6 (p < 0.001), tumour necrosis factor-α (p = 0.021), ESR (p = 0.001), CRP (p = 0.004), lactate dehydrogenase (p = 0.007), and creatine kinase (p = 0.004) at day 7 after surgery compared with conventional TKA. Robotic TKA was associated with significantly improved preservation of the periarticular soft tissue envelope (p < 0.001), and reduced femoral (p = 0.012) and tibial (p = 0.023) bone trauma compared with conventional TKA. Robotic TKA significantly improved the accuracy of achieving the planned limb alignment (p < 0.001), femoral component positioning (p < 0.001), and tibial component positioning (p < 0.001) compared with conventional TKA.

CONCLUSION

Robotic TKA was associated with a transient reduction in the early (day 7) postoperative inflammatory response but there was no difference in the immediate (< 48 hours) or late (day 28) postoperative systemic inflammatory response compared with conventional TKA. Robotic TKA was associated with decreased iatrogenic periarticular soft tissue injury, reduced femoral and tibial bone trauma, and improved accuracy of component positioning compared with conventional TKA. Cite this article: Bone Joint J 2021;103-B(1):113-122.

An insert with less than spherical medial conformity causes a loss of passive internal rotation after calipered kinematically aligned TKA

INTRODUCTION

In total knee arthroplasty (TKA), the level of conformity, a medial stabilized (MS) implant, needs to restore native (i.e., healthy) knee kinematics without over-tensioning the flexion space when the surgeon chooses to retain the posterior cruciate ligament (PCL) is unknown. Whether an insert with a medial ball-in-socket conformity and lateral flat surface like the native knee or a less than spherical medial conformity restores higher and closer to native internal tibial rotation without anterior lift-off, an over-tension indicator, when implanted with calipered kinematic alignment (KA), is unknown.

METHODS AND MATERIALS

Two surgeons treated 21 patients with calipered KA and a PCL retaining MS implant. Validated verification checks that restore native tibial compartment forces in passive flexion without release of healthy ligaments were used to select the optimal insert thickness. A goniometer etched onto trial inserts with the ball-in-socket and the less than spherical medial conformity measured the tibial rotation relative to the femoral component at extension and 90° and 120° flexion. The surgeon recorded the incidence of anterior lift-off of the insert.

RESULTS

The insert with the medial ball-in-socket and lateral flat surface restored more internal tibial rotation than the one with less than spherical medial conformity, with mean values of 19° vs. 17° from extension to 90° flexion (p < 0.01), and 23° vs. 20°-120° flexion (p < 0.002), respectively. There was no anterior lift-off of the insert at 90° and 120° flexion.

CONCLUSION

An MS insert with a medial ball-in-socket and lateral flat surface that matches the native knee's spherical conformity restores native tibial internal rotation when implanted with calipered KA and PCL retention without over-tensioning the flexion space.

Higher incidence of manipulation under anesthesia following TKA associated with the periarticular infiltration of a liposomal bupivacaine cocktail compared to a modified Ranawat cocktail

BACKGROUND

The purpose of this study was to compare the frequency of postoperative stiffness requiring manipulation under anesthesia (MUA) before and after switching from the intraoperative use of liposomal bupivacaine (LB).

METHODS

This was an institutional review board (IRB)-exempt retrospective cohort study (IRB#71733) on all patients who underwent primary total knee arthroplasty (TKA) by a single surgeon between April 2016 and December 2017. We compared 169 knees that received LB group to 167 knees that received a modified Ranawat cocktail (MR group). Perioperative care pathways remained consistent during the study period, as were requirements for MUA which included flexion range of motion below approximately 90 at 6-12 weeks. To compare the incidence of MUA between the groups, a population-averaged Poisson regression analysis was used.

RESULTS

The two groups were similar, with mean age of 63 (range 31-91) in the LB group and 64 (range 42-84) in the MR group, a preponderance of females in both groups (p = 0.866), similar preoperative knee flexion between groups (p = 0.162), and similar Patient-Reported Outcomes Measurement Information System scores. The frequency of MUA, however, was significantly lower in the MR group (LB: 7.7% [95% CI 3.7-12%] vs. MR: 2.4% [95% CI <1-4.7%] [IRR 3.2, 95% CI 1.08-9.76, p . 0.037]).

CONCLUSIONS

In summary, this is a novel report of a potentially previously unrecognized increased incidence of MUA associated with the use of LB compared with a MR cocktail. Given no other notable changes to the perioperative care or MUA thresholds following TKA, the reasons for these findings are unclear but deserve additional investigation.

[Adjusted mechanical alignment: operative technique-Tips and tricks]

INTRODUCTION

Mechanical alignment (MA) is a standardized procedure that aims to achieve a neutrally aligned leg axis. An alignment of the prosthesis closer to the patient's anatomy can be an approach for better clinical outcomes. The surgical technique of adjusted mechanical alignment (aMA) presented here is a modified extension-gap-first technique that takes into account the natural ligamentous tension of the knee joint so that ligamentous releases can be avoided as far as possible.

INDICATION

The aMA technique can be used for primary and secondary varus gonarthrosis of up to 20° of varus.

SURGICAL TECHNIQUE

The aim of the operation is to achieve a balanced ligament tension through a femoral osseous correction rather than ligament releases. TEA and the sulcus line are marked to control the ligament-based femoral rotation. The osteophytes are removed to ensure a reliable ligament tension. A quantitative ligament tensioner is stretched with great care, and gap width as well as medial and lateral ligament tension are read off. In order to correct an extension gap asymmetry, instead of the typical medial soft tissue release, the asymmetry is compensated by a special femoral cutting block. Now, the flexion gap is assessed, whereby the transverse femoral rotation follows the soft tissue tension. The tensioner adjusts a rectangular flexion gap with balanced ligament tension. After a final balancing of the gaps, the femoral preparation is completed and the trial components are inserted. Here, the rotation of the tibial component is set by repeated flexion-extension cycles.

DISCUSSION AND CONCLUSION

The technique presented combines a measured-resection technique with individual ligament tension. The maximum deviation of the femoral alignment in the coronal plane from the neutral alignment is 2.5°. In order to avoid problems, it is recommended, as with the described technique, to achieve a component alignment based on the patient anatomy by adjusting the femoral component. The measured-resection technique carries the risk of flexion instability. With the gap-balancing technique symmetrical ligament tension can be achieved, assuming precise proximal tibial cuts. When aligning the femoral component rotation, flexion gap stability and patella tracking should be considered. Long-term studies of high case numbers are necessary to evaluate the good short-term results of the presented surgical technique.

Bone resection for mechanically aligned total knee arthroplasty creates frequent gap modifications and imbalances

PURPOSE

The objective of this study was to calculate bone resection thicknesses and resulting gap sizes, simulating a measured resection mechanical alignment (MA) technique for total knee arthroplasty (TKA).

METHODS

MA bone resections were simulated on 1000 consecutive lower limb CT scans from patients undergoing TKA. Femoral rotation was aligned with either the surgical trans-epicondylar axis (TEA) or with 3° of external rotation to the posterior condyles (PC). Imbalances in the extension space, flexion space, medial compartment and lateral compartment were calculated.

RESULTS

Extension space imbalances (≥ 3 mm) occurred in 25% of varus and 54% of valgus knees and severe imbalances (≥ 5 mm) were present in up to 8% of varus and 19% of valgus knees. Higher flexion space imbalance rates were created with TEA versus PC (p < 0.001). Using TEA, only 49% of varus and 18% of valgus knees had < 3 mm of imbalance throughout the extension and flexion spaces, and medial and lateral compartments.

CONCLUSION

A systematic use of the simulated measured resection MA technique for TKA leads to many cases with imbalance. Some imbalances may not be correctable surgically and may result in TKA instability. Modified versions of the MA technique or other alignment methods that better reproduce knee anatomies should be explored.

LEVEL OF EVIDENCE

2.

Tightening medial collateral ligament during total knee arthroplasty for patients with fixed valgus deformity: A novel technique

BACKGROUND

This study aimed to explore a new surgical technique for gap balance by tightening the medial collateral ligament (MCL) in total knee arthroplasty (TKA) in patients with fixed valgus deformity.

MATERIALS AND METHODS

A prospective analysis was performed on 15 patients (16 knees) with a fixed valgus deformity that was corrected by tightening the MCL during TKA. A single surgeon performed all the 16 TKAs using nonconstrained posterior substituting implant, with two knees treated with long-stem tibial prosthesis. Clinical scores, knee stability, and radiographic evaluations were recorded preoperatively and postoperatively.

RESULTS

Complete weight-bearing could be carried out under the protection of the brace postoperatively. At the third month after surgery, X-rays showed the brace was not worn. The mean follow-up was 26.6 months (range 12-42 months). The average preoperative mechanical axis was 15.4 ± 2.3° (range 11-25°), and postoperatively it was 0.6 ± 0.1° (range 0-2°). No complication relative to the technique occurred.

CONCLUSION

This new surgical technique has demonstrated excellent early clinical results and can be a good supplement for fixed valgus knee arthroplasty. Level of Evidence: III.

The Role of Complete Posterior Cruciate Ligament Release in Flexion Gap Balancing for Total Knee Arthroplasty

BACKGROUND

The sequence of posterior cruciate ligament (PCL) release in posterior-substituting designs, when performing gap balancing in total knee arthroplasty (TKA), is variable. We hypothesize that early complete PCL release during knee exposure will change the flexion balance to result in a uniform medial-lateral flexion gap symmetry at the time of implant placement.

METHODS

Ten cadaveric knees were prepared for TKA using standard medial parapatellar approach. Medial and lateral flexion gaps were measured in the conditions of intact, partial (50%) resection, and full resection of PCL. Measurements were performed with both surgical navigation and a caliper. Flexion gap distances were reported for medial and lateral compartments in the 3 PCL conditions.

RESULTS

Medial flexion gap increased after only complete release of the PCL (mean 3.94-5.05 mm). The lateral flexion gap increased as well (mean 4.17-4.67 mm). Complete PCL release resulted in a statistically significant increase in medial flexion gap compared to intact (P = .013) and partially released (P = .012) specimens. No significant differences were noted in lateral flexion gap change. Notable change in medial versus lateral gap (flexion gap symmetry) relationship occurred after just partial PCL release (P = .018).

CONCLUSION

Among the 3 PCL states, changes in flexion gap distance were most conspicuous in the medial compartment. This suggests gap balancing performed with incomplete PCL release will not accurately reflect gap distance after eventual PCL removal, thus supporting the hypothesis. It is recommended that the PCL should be released to the fullest extent possible before ligament tensioning for femoral component rotation in posterior-stabilized TKA.

Under-corrected knees do not fail more than aligned knees at 8 years in fixed severe valgus total knee replacement

PURPOSES

A fixed severe valgus knee is a surgical challenge. A safe post-operative Hip-Knee-Ankle angle (HKA) range of 180° ± 4 was recommended, but recent studies mentioned equal results from outliers of this range. Nevertheless, no distinction was made between varus and valgus knees, as well as over-corrected or under-corrected knees. Did post-operative nonaligned total knee replacements (TKR) from fixed severe valgus knees behave differently from the properly aligned population? Did over-corrected knees behave differently from under-corrected knees?

METHODS

Through a multi-center retrospective cohort study, we provided 557 knees of at least 10° of minimal pre-operative valgus; in this population 75 presented a post-operative Hip-Knee-Ankle angle (HKA) outside of the 180° ± 4 range; 23 of them had at least 5° of varus; 52 of them had at least 5° of valgus. Median pre-operative HKA of the entire cohort was 194° (range 190-198). Median follow-up was 8 years (range 5-11); Knee Society Score (KSS) results, HKA, Femoral and Tibial Mechanical Angles (FMA, TMA) and complication rates were obtained. The outlier group (HKA ≤ 175 or ≥ 185) was compared to the control group (HKA 180 ± 4); over-corrected (HKA ≤ 175) and under-corrected (HKA ≥ 185) sub-groups were individually tested against the control group.

RESULTS

The outlier group had a lower Final Knee Score than the aligned group (p = 0.023). In the over-corrected sub-group, median post-operative FMA was 88° (SD 4°) and median TMA was 87° (SD 4°). The complication rate was higher (p = 0.019). Knee (p = 0.018), Function (p = 0.034) and Final Knee Scores (p = 0.03) were statistically lower than in the control group. In the under-corrected sub-group, mean post-operative FMA was 93° (SD 2°) and mean TMA was 91° (SD 2°). The complication rate was lower (p = 0.019) and there was no difference with the control group concerning KSS.

CONCLUSIONS

In case of pre-operative fixed severe valgus knee, one should avoid over-correcting HKA angle and especially the TMA. Over-correction of a severe preoperative valgus in a post-operative varus was prejudicial for TKA survival. Keeping a severe valgus knee in low valgus to avoid using a more constrained implant and/or ligament releases will not decrease the 5-10 year implant survival and functional scores.

LEVEL OF EVIDENCE

Level IV-Case series.

Laxity Profiles in the Native and Replaced Knee-Application to Robotic-Assisted Gap-Balancing Total Knee Arthroplasty

BACKGROUND

The traditional goal of the gap-balancing method in total knee arthroplasty is to create equal and symmetric knee laxity throughout the arc of flexion. The purpose of this study was to (1) quantify the laxity in the native and the replaced knee throughout the range of flexion in gap-balancing total knee arthroplasty (TKA) and (2) quantify the precision in achieving a targeted gap profile throughout flexion using a robotic-assisted technique with active ligament tensioning.

METHODS

Robotic-assisted, gap-balancing TKA was performed in 14 cadaver specimens. The proximal tibia was resected, and the native tibiofemoral gaps were measured using a robotic tensioner that dynamically tensioned the soft-tissue envelope throughout the arc of flexion. The femoral implant was then aligned to balance the gaps at 0° and 90° of flexion. The postoperative gaps were then measured during final trialing with the robotic tensioner and compared with the planned gaps.

RESULTS

The native gaps increased by 3.4 ± 1.7 mm medially and 3.7 ± 2.1 mm laterally from full extension to 20° of flexion (P < .001) and then remained consistent through the remaining arc of flexion. Gap balancing after TKA produced equal gaps at 0° and 90° of flexion, but the gap laxity in midflexion was 2-4 mm greater than at 0° and 90° (P < .001). The root mean square error between the planned gaps and actual measured postoperative gaps was 1.6 mm medially and 1.7 mm laterally throughout the range of motion.

CONCLUSION

Aiming for equal gaps at 0° and 90° of flexion produced equal gaps in extension and flexion with larger gaps in midflexion. Consistent soft-tissue balance to a planned gap profile could be achieved by using controlled ligament tensioning in robotic-assisted TKA.

Iatrogenic Bone and Soft Tissue Trauma in Robotic-Arm Assisted Total Knee Arthroplasty Compared With Conventional Jig-Based Total Knee Arthroplasty: A Prospective Cohort Study and Validation of a New Classification System

BACKGROUND

The objective of this study was to compare macroscopic bone and soft tissue injury between robotic-arm assisted total knee arthroplasty (RA-TKA) and conventional jig-based total knee arthroplasty (CJ-TKA) and create a validated classification system for reporting iatrogenic bone and periarticular soft tissue injury after TKA.

METHODS

This study included 30 consecutive CJ-TKAs followed by 30 consecutive RA-TKAs performed by a single surgeon. Intraoperative photographs of the femur, tibia, and periarticular soft tissues were taken before implantation of prostheses. Using these outcomes, the macroscopic soft tissue injury (MASTI) classification system was developed to grade iatrogenic bone and soft tissue injuries. Interobserver and Intraobserver validity of the proposed classification system was assessed.

RESULTS

Patients undergoing RA-TKA had reduced medial soft tissue injury in both passively correctible (P < .05) and noncorrectible varus deformities (P < .05); more pristine femoral (P < .05) and tibial (P < .05) bone resection cuts; and improved MASTI scores compared to CJ-TKA (P < .05). There was high interobserver (intraclass correlation coefficient 0.92 [95% confidence interval: 0.88-0.96], P < .05) and intraobserver agreement (intraclass correlation coefficient 0.94 [95% confidence interval: 0.92-0.97], P < .05) of the proposed MASTI classification system.

CONCLUSION

There is reduced bone and periarticular soft tissue injury in patients undergoing RA-TKA compared to CJ-TKA. The proposed MASTI classification system is a reproducible grading scheme for describing iatrogenic bone and soft tissue injury in TKA.

CLINICAL RELEVANCE

RA-TKA is associated with reduced bone and soft tissue injury compared with conventional jig-based TKA. The proposed MASTI classification may facilitate further research correlating macroscopic soft tissue injury during TKA to long-term clinical and functional outcomes.

Preoperative Valgus Alignment Does Not Predict Inferior Outcome of Total Knee Arthroplasty

BACKGROUND

Preoperative valgus deformity is present in an estimated 10-20% of patients undergoing total knee replacement (TKR).

QUESTIONS/PURPOSES

The objective of this study was to compare the Western Ontario and McMaster Universities Arthritis Index (WOMAC) scores after TKR in a matched cohort of patients with preoperative valgus and varus deformities.

METHODS

This is a matched cohort study of 162 patients with varus native knees and 162 patients with valgus native knees who underwent TKR and were prospectively followed in our institutional registry. Patients matched were based on age, BMI, sex, and severity of preoperative knee deformity, which was classified as mild, moderate, severe varus or valgus, or no deformity. Outcomes were evaluated using the WOMAC preoperatively and at 6 weeks, 3 months, 6 months, and 1 year postoperatively.

RESULTS

No significant difference was found between the matched varus and valgus cohorts in all WOMAC subdomain scores except for a marginally worse stiffness at 1 year in patients with valgus deformity (WOMAC stiffness, 75.1 varus vs. 70.1 valgus; P = 0.049). This is below the minimal clinically important difference for WOMAC scores. There was no significant difference in postoperative varus/valgus alignment between the two groups (P = 0.092).

CONCLUSION

We found no clinically significant difference in any of the WOMAC domains in patients with preoperative varus deformity versus valgus deformity within the first year after TKR. These findings may allow surgeons to more appropriately counsel patients with osteoarthritis with valgus deformity that they can expect similar outcomes compared to patients with varus deformity.

Does alignment of the limb and tibial width determine relative narrowing between compartments when planning mechanically aligned TKA?

INTRODUCTION

We determined (1) the range of the hip-knee-ankle (HKA) angle in the native or pre-arthritic limbs of patients with a contralateral total knee arthroplasty (TKA); and when mechanical alignment is planned (2) the relationships between the HKA angle and the tibial width, and the relative narrowing between the medial and lateral compartments and (3) the effect of tibial width on the range of narrowing.

METHODS

The HKA angle, distal lateral femoral angle (DLFA), and proximal medial tibial angle (PMTA) were measured on the native limb of 102 subjects (53 female) treated with contralateral TKA. The sine of the angle of the resection gap (PMTA minus 90° subtracted from the DLFA minus 90°) multiplied by the tibial width and by narrow (59 mm), average (75 mm), and wide (91 mm) tibias computed relative narrowing.

RESULTS

The HKA angle ranged from 8° varus to - 7° valgus; 20% had constitutional varus (≥ 3°) and 11% constitutional valgus (≤ - 3°). The HKA angle strongly predicted (r ² = 0.87) and tibial width weakly predicted (r ² = 0.06) relative narrowing. For narrow, average, and wide tibias, the maximum medial narrowing was 9, 11, 14 mm and maximum lateral narrowing was 7, 9, and 11 mm, respectively (p < 0.0001).

CONCLUSION

When mechanical alignment is planned, there is greater relative narrowing between compartments when the pre-arthritic limb greatly deviates from a 0° HKA angle and the tibia is wide. These limbs may need soft-tissue releases until neutral postoperative limb alignment of 0° and negligible varus-valgus laxity are achieved.

LEVEL OF EVIDENCE

IV, therapeutic study.

Preoperative radiographic valgus alignment predicts the extent of lateral soft tissue release and need for constraint in valgus total knee arthroplasty

BACKGROUND

In total knee arthroplasty (TKA) for valgus knees, the decision to use a constrained implant is often made intraoperatively depending on the extent of soft tissue releases performed and residual soft tissue imbalance. The purpose of this study is to determine if preoperative radiographic criteria of valgus knees can predict the extent of soft tissue releases required and the level of constraint needed to balance the knee during TKA.

METHODS

A single surgeon's 807 consecutive TKA standing hip-knee-ankle radiographs from 2007-2012 were analyzed. One hundred eighty-seven valgus knees were identified and annotated. Statistical univariate and multivariate analyses were performed for both outcomes, lateral release and articulation, to assess the association with risk factors of gender, age, and preoperative radiographic markers of valgus deformity. A P-value <.05 represented a significant difference between groups.

RESULTS

Use of a constrained articulation was associated with increased valgus deformity (mechanical hip-knee-ankle angle, P < .0001) and extent of lateral soft tissue release (P < .0001). No relationship existed between the use of a constrained articulation and age or gender (P > .05). A preoperative anatomic tibiofemoral valgus angle of >16.8° was associated with the use of a constrained articulation during surgery.

CONCLUSIONS

Our data demonstrate that preoperative radiographic characteristics of the valgus knee can be utilized to predict the extent of lateral soft tissue release and whether a constrained articulation will be required in TKA. This will provide surgeons with useful information to offer accurate preoperative counseling to patients and to ensure that the appropriate prosthetic parts are available during surgery.

Unconstrained total knee arthroplasty in significant valgus deformity: a modified surgical technique to balance the knee and avoid instability

PURPOSE

Correction of valgus deformity in total knee arthroplasty (TKA) is technically challenging and has produced variable results. A modified surgical technique involving adapting the distal femoral cut with minimal soft tissue release is proposed. The authors hypothesise that using this technique would result in satisfactory radiological and functional outcome.

METHODS

The technique involves balancing the knee in extension by changing the distal femoral resection angle and confining soft tissue release to only the posterolateral capsule if required. Retrospective analysis of 276 consecutive TKAs performed using this technique under the care of a single surgeon in patients with valgus knee deformity ≥10° was undertaken. An unconstrained mobile bearing implant was used in all knees with a medial para-patellar approach, and outcome scores were collected prospectively. Seventy-five percent of the knees were cementless. [corrected]

RESULTS

Mean coronal alignment of the lower limb was corrected from 15.6° (±5.7°) to 3.8° (±2.5°). 97.8 % knees had their coronal alignment restored to ≤7°. Seventy-eight knees (28 %) were balanced by only changing the distal femoral resection angle. One hundred and ninety-eight knees (72 %) had release of the posterolateral capsule. Sixteen knees (5.8 %) also had release of iliotibial band. Lateral patellar release was performed in 39 knees (14 %). 93.1 % had central patello-femoral alignment. At between 5.8 and 10.5 year follow-up, there has been one spinout, managed by closed reduction, and one revision of tibial tray for subsidence. The mean American Knee Society clinical score improved from 19.1 to 86.5 (±12.2).

CONCLUSION

Adequate correction of valgus knee deformity was successfully achieved using this modified technique with satisfactory medium-term outcome and avoidance of instability.

Surgical Techniques for Total Knee Arthroplasty: Measured Resection, Gap Balancing, and Hybrid

Total knee arthroplasty (TKA) is effective in managing end-stage degenerative joint disease. Achieving favorable clinical outcomes is predicated on proper implant alignment, sizing, and rotation as well as adequate soft-tissue balancing. Modern TKA implants are designed to address the fundamental needs of attaining stability in both flexion and extension and of optimizing patellar tracking. Measured resection and gap balancing are the two different techniques used to implant the TKA components used today. Both techniques have been validated as durable and successful, and each has unique advantages and disadvantages. A hybrid technique has been developed that combines the benefits of measured resection and gap balancing and minimizes the limitations associated with both techniques. This hybrid approach has the potential for achieving improved TKA kinematics and refined surgical technique.

Soft Tissue Releases in Total Knee Arthroplasty for Valgus Deformities

BACKGROUND

Primary total knee arthroplasty (TKA) for valgus knee deformities can be challenging. Soft tissue releases are often necessary to achieve a well-balanced knee. We reviewed the frequency of soft tissue releases including lateral retinacular release (LRR) as it pertains to preoperative limb alignment. Postoperatively, we evaluated limb alignment, knee range of motion, and complications.

METHODS

From 2010 to 2016, 214 primary TKAs with valgus deformity were performed by a single surgeon. One hundred eighty-one patients had an average follow-up of 24 months. For these patients, clinical data including preoperative and postoperative range of motion, complications, and revision rates were collected. Soft tissue releases, preoperative and postoperative limb axis deviation, and level of prosthetic constraint were recorded in all patients regardless of length of follow-up.

RESULTS

There were 33 knees (15%) that required 1 release, 69 knees (32%) required 2 releases, 81 knees (38%) required 3 releases, and 31 knees (14%) that required 4 or more releases. The average preoperative mechanical axis was 9.4°, and the average postoperative mechanical axis was 0.13°. There were 85 knees (40%) that required an LRR. Increased severity of preoperative deformity correlated with the need for more soft tissue release, but did not correlate with the need for LRR. No knees were revised for instability. No patella complications resulted from LRR.

CONCLUSION

Selective soft tissue release for primary valgus TKA was effective without increasing prosthetic constraint. Severe deformities required more soft tissue releases. LRR can be frequently used with minimal complications.

Correcting deformity in total knee arthroplasty

Collateral ligament release is advocated in total knee arthroplasty (TKA) to deal with significant coronal plane deformities, but is also associated with significant disadvantages.

We describe steps to avoid release of the collateral (superficial medial and lateral collateral) ligaments during TKA in severely deformed knees, while correcting deformity and balancing the knee.

Cite this article: Bone Joint J 2016;98-B(1 Suppl A):101–4.

Articular contact kinematics of the knee before and after a cruciate retaining total knee arthroplasty

Accurate knowledge of tibiofemoral articular contact kinematics of the knee after total knee arthroplasty (TKA) is important for understanding the intrinsic knee biomechanics and improving the longevity of the components. The objective of this study was to compare the in vivo articular contact kinematics of the knees with end-stage medial osteoarthritis (OA) during a weight-bearing, single leg lunge activity before and after a posterior cruciate retaining TKA (CR-TKA) using a dual fluoroscopic imaging technique. We found that the CR-TKA resulted in more posterior contact positions on the tibial surface and a reduced range of motion in the medial and lateral compartments. The distances between medial and lateral contact locations in the CR-TKA knees were statistically larger than the OA knees. The articular contact centers have shifted from medial side of the tibial plateau pre-operatively to the lateral side after operation. This study indicated that the CR-TKA resulted in significant changes in contact kinematics of the knees in both anteroposterior and mediolateral directions. Further studies are needed to determine the influence of the altered in vivo contact kinematics on the longevity of polyethylene liner and long term clinical outcomes of the TKA.

The effect of flexion balance on functional outcomes in cruciate-retaining total knee arthroplasty

PURPOSE

We investigated the relations between flexion balances and functional outcomes after total knee arthroplasty (TKA).

METHODS

Sixty-one knees that underwent a TKA were included in this study. Clinical assessments were performed and flexion balances of the knee were assessed on varus and valgus stress radiographs at 90° of knee flexion. Total laxity was defined as the sum of medial and lateral laxities. Knees were divided into balanced (≤3°, n = 51) and unbalanced (>3°, n = 10) groups based on the only difference of mediolateral laxity regardless of total laxity. And the balanced group was divided into Grade I (<6°), Grade II (≥6° but ≤10°) or Grade III (>10°) groups based on the amount of total laxity.

RESULTS

Although no statistically significant differences were observed between the balanced and unbalanced groups in terms of range of motion (ROM) and KS pain scores, the balanced group achieved better results in terms of KS function and WOMAC scores than the unbalanced group. Total laxity was significantly less in the balanced group. In addition, Grade II knees in the balanced group had significantly better KS pain and function scores, and WOMAC scores than Grade Ior Grade III knees.

CONCLUSIONS

These results suggest that total knees with good balanced flexion stability can provide good functional outcomes after TKA.

Efficacy and safety of extracorporeal shock wave therapy for orthopedic conditions: a systematic review on studies listed in the PEDro database

BACKGROUND

Extracorporeal shock wave therapy (ESWT) is an effective and safe non-invasive treatment option for tendon and other pathologies of the musculoskeletal system.

SOURCES OF DATA

This systematic review used data derived from the Physiotherapy Evidence Database (PEDro; www.pedro.org.au, 23 October 2015, date last accessed).

AREAS OF AGREEMENT

ESWT is effective and safe. An optimum treatment protocol for ESWT appears to be three treatment sessions at 1-week intervals, with 2000 impulses per session and the highest energy flux density the patient can tolerate.

AREAS OF CONTROVERSY

The distinction between radial ESWT as 'low-energy ESWT' and focused ESWT as 'high-energy ESWT' is not correct and should be abandoned.

GROWING POINTS

There is no scientific evidence in favour of either radial ESWT or focused ESWT with respect to treatment outcome.

AREAS TIMELY FOR DEVELOPING RESEARCH

Future randomized controlled trials should primarily address systematic tests of the aforementioned optimum treatment protocol and direct comparisons between radial and focused ESWT.