Remaining mild varus limb alignment leads to better clinical outcome in total knee arthroplasty for varus osteoarthritis

Postero-Central Slice Osteotomy of the Proximal Tibia: A Novel Technique for Correcting Resistant Tight Extension Gaps in Posterior-Stabilized Total Knee Arthroplasty for Varus Osteoarthritis

BACKGROUND

The aim of total knee arthroplasty (TKA) is to circumvent the pain due to advanced osteoarthritis of the knee joint and correct the limb alignment and biomechanics to improve patients' quality of life. Apart from medio-lateral balancing, balancing flexion and extension gaps is a prerogative to achieve good results. This study proposes a novel surgical technique of postero-central slice osteotomy of the proximal tibia (PCSO-PT) for correcting tight extension gaps in posterior-stabilized knees and assesses its clinical and functional outcomes.

METHODS

A prospective study was conducted on 84 consecutive knees with tricompartmental osteoarthritis and varus deformity, requiring PCSO-PT during posterior-stabilized TKA between January 2016 and July 2018. Knee Society scores, flexion deformity, range of motion, antero-posterior instability, and complications were assessed at regular intervals for a minimum of 2 years postoperatively.

RESULTS

Residual flexion deformities less than 11° after posterior capsular release were successfully corrected by the osteotomy. The mean preoperative flexion deformity of 18.1 ± 2.5° improved to 8.6 ± 2.2° intraoperatively after posterior capsular release from the femoral end and to 0.65 ± 0.76° intraoperatively immediately after the osteotomy, with no residual flexion deformity noted in any patient 6 weeks postoperatively. It had no negative effect on the significant post-TKA improvement of the mean Knee Society score from 32 ± 12 preoperatively to 94 ± 3 at the terminal follow-up. A direct correlation between preoperative flexion deformity and a resistant, tight extension gap (P = 0.003) was noted. There was no increase in coronal plane or sagittal plane instabilities in midflexion or on mobilization throughout the follow-up period, nor were any major adverse effects noted in this period.

CONCLUSIONS

A PCSO-PT is an effective and safe alternative to overcoming tight extension during TKA after femoral-end capsular release, instead of capsular release from the tibial end or midcapsular region.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

Mechanically aligned total knee arthroplasty does not yield uniform outcomes across all coronal plane alignment of the knee (CPAK) phenotypes

PURPOSE

Patient dissatisfaction rates following total knee arthroplasty (TKA) reported in the literature reach 20%. The optimal coronal alignment is still under debate. The aim of this retrospective study was to compare clinical outcomes in different coronal plane alignment of the knee (CPAK) phenotypes undergoing mechanically aligned (MA) TKA. The hypothesis was that knees with preoperative varus arithmetic hip-knee-ankle angle (aHKA) would achieve inferior clinical outcomes after surgery compared to other aHKA categories. Additionally, another objective was to assess CPAK phenotypes distribution in the study population.

METHODS

A retrospective selection was made of 180 patients who underwent MA TKA from April 2021 to December 2022, with a 1-year follow-up. Coronal knee alignment was classified according to the CPAK classification. Clinical outcome evaluations were measured using the Knee Society Score (KSS), Oxford Knee Score (OKS), Short Form Survey 12 and Forgotten Joint Score (FJS). Differences in clinical outcomes were considered statistically significant with a p value <0 .05.

RESULTS

Patients with varus aHKA achieved significantly inferior outcomes at final follow-up compared to other aHKA categories in KSS pt. 1 (79.7 ± 17.2 vs. 85.6 ± 14.7; p = 0.028), OKS (39.2 ± 9.2 vs. 42.2 ± 7.2; p = 0.019) and FJS (75.4 ± 31.0 vs. 87.4 ± 22.9; p =0 .003). The most common aHKA category was the varus category (39%). The most common CPAK phenotypes were apex distal Types I (23.9%), II (22.8%) and III (13.3%).

CONCLUSION

MA TKA does not yield uniform outcomes across all CPAK phenotypes. Varus aHKA category shows significantly inferior results at final follow-up. The most prevalent CPAK categories are varus aHKA and apex distal JLO, with phenotypes I, II and III being the most common. However, their gender distribution varies significantly.

LEVEL OF EVIDENCE

Level IV.

The Long-term Efficacy of Total Knee Arthroplasty on End-stage Kashin-Beck Disease of the Knee in Highland Tibetan Areas Patients: A Retrospective Study with 10-Year Follow-up

OBJECTIVE

Despite the established success of total knee arthroplasty (TKA) with end-stage osteoarthritis, there is a notable scarcity of research on its long-term outcomes in individuals suffering from end-stage Kashin-Beck disease (KBD). This retrospective study aimed to assess the long-term outcomes and effectiveness of clinical function, quality of life, and complications of TKA and end-stage KBD patients in Tibetan highland areas.

METHODS

The retrospective cohort included 43 KBD patients, comprising a total of 59 knees, who had undergone TKA at West China Hospital, Sichuan University between 2008 and 2021. Patients were subsequently followed up for a minimum of 3 years, and received rigorous radiological and clinical assessments at 3, 6, and 12 months post surgery, followed by annual examinations thereafter. The evaluation included various efficacy indices, including visual analogue scale (VAS) scores, hospital for special surgery (HSS) scores, functional score for adult Tibetans with Kashin-Beck disease (FSAT-KBD), and radiographic findings. Comparison of indicators within the same group was conducted using one-way repeated-measures analysis of variance or paired sample t-tests, whereas between-group differences were compared using an independent t-test.

RESULTS

Throughout the average follow-up duration of 10.8 years, patients experienced a substantial reduction in knee pain and noteworthy functional improvement. The VAS scores decreased significantly from 77.47 ± 4.12 mm before surgery to 10.91 ± 1.97 mm after surgery, indicating considerable alleviation of knee pain. The HSS scores improved markedly, increasing from 44.26 ± 4.95 preoperatively to 91.26 ± 4.37, indicating enhanced joint function. Similarly, the FSAT-KBD exhibited positive progression, increasing from 25.90 ± 3.12 to 36.95 ± 3.54. Importantly, at the last follow-up, none of the patients presented with periprosthetic infection, prosthesis loosening, or periprosthetic fracture.

CONCLUSION

At long-term follow-up, compared with patients in the preoperative period, patients in Tibetan highland areas with KBD of the knee who underwent TKA benefited from a significant reduction in pain, improvement in joint function, and satisfactory improvement in quality of life.

Comparison of Outcomes in Obese Patients after Total Knee Arthroplasty with Neutral or Mild Varus: A Retrospective Study with 8-Year Follow-Up

OBJECTIVES

Residual varus after total knee arthroplasty (TKA) can affect functional outcomes, which may worsen in the presence of obesity. However, no studies were found to compare the outcomes of obese patients involving postoperative residual mild varus or neutral. The aim of this study was to compare postoperative complications and prosthesis survival, and functional outcomes for knees of obese patients with neutral or mild varus after TKA.

METHODS

We retrospectively reviewed 188 consecutive obese patients (body mass index ≥30 kg/m2) at our hospital who underwent TKA due to varus knee osteoarthritis from January 2010 to December 2015. The mechanical hip-knee-ankle axis angle was measured in all patients at admission and discharge. Knee functions were retrospectively assessed based on the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, Knee Society Knee Score (KS-KS), Knee Society Function Score (KS-FS), Forgotten Joint Score (FJS), and range of motion (ROM). Continuous data were compared between knees with neutral or mild varus alignment using analysis of Student's t test or variance or the Kruskal-Wallis test as appropriate. For multiple comparisons of outcomes, we used Bonferroni-Dunn method to adjust p-values. Categorical data were compared using the chi-squared test.

RESULTS

Of the 156 knees in 137 obese patients who completed follow-up for a mean of 8.32 ± 1.47 years, 97 knees were corrected from varus to neutral and 54 knees were kept in mild residual varus. Patients with mild varus knees had significantly WOMAC (8.25 ± 8.637 vs. 14.97 ± 14.193, p = 0.009) and better FJS (86.03 ± 15.607 vs. 70.22 ± 30.031, p = 0.002). The two types of knees did not differ significantly in KS-KS, KS-FS, or ROM. Although one patient with a neutral knee had to undergo revision surgery, there was no significant difference between two groups.

CONCLUSIONS

For obese patients with osteoarthritis, preservation of residual varus alignment after TKA can improve functional outcomes without compromising prosthesis survival.

Why Kinematic Alignment Makes Little Sense in Valgus Osteoarthritis of the Knee: A Narrative Review

There is a debate about the best alignment strategies in total knee arthroplasty (TKA). Mechanical alignment (MA) targets in combination with necessary soft tissue releases are the gold standard for TKA in end-stage valgus osteoarthritis. Some authors propagate kinematic alignment (KA) with the aim of restoring the patient's native alignment and minimizing the need for soft tissue releases. Our previous studies showed that MA with standardized soft tissue release produces reproducible results, and that the preoperative phenotype does not influence the results of patients with valgus osteoarthritis. These data suggest that there is no functional advantage to preserving valgus alignment in patients with valgus osteoarthritis. Many patients with valgus osteoarthritis present with a compromised medial collateral ligament and leaving the knee in valgus could increase the risk of secondary instability. The current literature supports MA TKA with soft tissue release as the gold standard. While using more sophisticated enabling technologies like robotic surgery might allow for aiming for very slight (1-2°) valgus alignment on the femoral side, any valgus alignment outside this range should be avoided. This review paper summarizes our current knowledge on the surgical techniques of TKA in patients with valgus osteoarthritis.

How Do the Morphological Abnormalities of Femoral Head and Neck, Femoral Shaft and Femoral Condyle Affect the Occurrence and Development of Medial Knee Osteoarthritis

OBJECTIVE

At present, the main viewpoint is that tibial varus is the main reason of medial knee osteoarthritis (OA), and high tibial osteotomy (HTO) is also the main alignment correction method to correct medial knee OA. In contrast, the impact of the anatomical alignment of the femur on medial knee OA is often overlooked. We evaluated the increased risk for medial knee OA because a varus alignment could be attributed to the anatomical reasons that include hip anatomy, femoral shaft bowing (FSB) and femoral condylar dysplasia.

METHODS

The present research adopted a cross-sectional study method. We selected 62 patients with HTO in the Third Hospital of Hebei Medical University from June 2021 to March 2022 as the HTO group and 55 healthy volunteers as the control group. Femoral neck-shaft angle (NSA), lateral FSB, mechanical lateral distal femoral angle (mLDFA) and hip-knee-ankle (HKA) was radiographically examined within the two groups. The femoral neck length and offset were also measured, and the ratio is represented by the ratio of the femoral neck length to off-set (N/O). The 2-tailed Student t-test was used to compare the differences between groups when the data were in accordance with a normal distribution. Otherwise, the Mann-Whitney U tests was used to compare the differences between groups.

RESULT

Compared to the control group, the HTO group had a higher offset (p < 0.05), greater femoral neck length (p < 0.05), and decreased (more varus) NSA (p < 0.05). The HKA in the HTO group was 172.20 ° (3.50°), which was significantly lower than that of the control group 177.00° (3.05°), (p < 0.001), while the medial OA was associated with more varus HKA. The mean mLDFA was 89.10 ° (2.35°) and 87.50° (2.85°) in the HTO and control groups (p < 0.005), respectively. The mean lateral FSB values of the full-length radiographs were larger (p < 0.001) in the HTO group (4.24° ± 3.25°) than that in control group (1.16° ± 2.32°).

CONCLUSION

The reduction of NSA (coxa vara) and the increase of the mLDFA can lead to medial knee OA, while the lateral FSB also affects medial OA. We believe that femoral deformity is also one of the cause of the medial knee OA. Therefore, it is necessary to evaluate the joint deformity of the femur and tibia before surgery in order to determine whether to use HTO alone to correct the lower limb alignment.

Individual Phenotype Does Not Impact the Outcome of Mechanical Aligned Total Knee Arthroplasties for Valgus Osteoarthritis

Background and Objectives: There is an ongoing discussion about the best alignment targets in total knee arthroplasty (TKA). Mechanical alignment has been the standard in TKA for years. Alongside the development of various classification systems to describe the native alignment of the knee (knee phenotype), kinematic alignment restoring the individual phenotype of the knee has been advocated more recently. Alignment in TKA becomes even more challenging in knees with preoperative deformities such as valgus osteoarthritis. Materials and Methods: The study retrospectively evaluated 158 knees in 135 patients who underwent TKA with a mechanical alignment target for valgus osteoarthritis. Pre- and postoperative hip knee angle, lateral distal femur angle, and medial proximal tibial angle/tibial plate angle (pre-/postoperative) were measured on standing hip-to-ankle radiographs. Knees were grouped according to the coronal plane alignment of the knee (CPAK) classification. Preoperative and postoperative range of motion and patient-related outcome measures (WOMAC, UCLA, SF-12, pain) were assessed. Results: There was no difference in outcome for mechanically aligned TKA between the different CPAK phenotypes, suggesting that mechanical alignment is an appropriate target for the different phenotypes analyzed in the study. Remaining valgus alignment was associated with decreased postoperative UCLA scores and decreased improvement in SF-12 scores (p = 0.011/p = 0.028). Within CPAK III, mechanical aligned TKA showed better postoperative UCLA Scores than TKA with valgus alignment (p = 0.015). The individual knee phenotype in patients with valgus osteoarthritis did not influence the outcome of mechanical aligned TKA operated with standardized soft-tissue release.

Effect of total knee arthroplasty for valgus knee correction on clinical outcome and patellar position

PURPOSE

The purpose was to investigate the effect of different degrees of valgus deformity correction on patellar position and clinical outcome in patients with valgus knees after total knee arthroplasty (TKA).

METHODS

We retrospectively analyzed and followed 118 patients with valgus knees. Based on the post-operative hip-knee-ankle (HKA), patients were divided into three groups: neutral (±3°), mild (3-6°), and severe (> 6°). Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), range of motion (ROM), and Knee Society Score (KSS) were used to evaluate post-operative clinical efficacy. Also, the patellar tilt angle (ε-angle), congruence angle (θ-angle), and Insall-Salvati index (ISI) were used to represent the patellar position. Post-operative observation indicators included HKA, angle of the femur (α-angle), tibial angle (β-angle), femoral component flexion angle (γ-angle), and tibial component posterior slope angle (δ-angle).

RESULTS

All patients showed significant improvements in HKA, ROM, WOMAC, and KSS after operation (P < 0.001). Regarding patellar position, the ISI values decreased to varying degrees (P < 0.05). The patellar tilt angle was significantly increased in the severe valgus group compared to that in the mild valgus and neutral groups (P < 0.001). Univariate analysis showed that the degree of post-operative residual valgus was significantly affected by WOMAC, KSS, α-, ε-, and θ-angles.

CONCLUSION

Minor valgus undercorrection did not affect the short-term outcome after TKA; however, when the residual valgus angle was > 6°, the post-operative scores were significantly reduced. Inadequate valgus correction does not result in significant changes in patellar height but may increase the risk of poor patellar tracking.

Difference Between Screw Cement Filling and Adequate Osteotomy With Thick Liner for Primary Primary Total Knee Arthroplasty in Patients With Rand IIb Tibial Defects

BACKGROUND

The effectiveness of 2 treatment options, screw-cement fill, and adequate osteotomy with a thick liner, in treating patients with Rand IIb tibial defects (tibial plateau defects to a depth of 5 to 10 millimeters) in primary total knee arthroplasty (TKA) has not yet been demonstrated. Therefore, we performed a retrospective study to evaluate the differences between these 2 treatments.

METHODS

We retrospectively analyzed patients who underwent primary TKA for Rand IIb tibial plateau defects from 2015 to 2020 from a department database. Patients were categorized into the screw-cement and thick liner groups based on the different options used to repair tibial defects. We evaluated Knee Society Score, range of motion (ROM), Insall-Salvati index (ISI), and Forgotten Joint Score (FJS) in both groups. We also compared differences in prosthesis survival, stiffness, myasthenia, and joint clicking between the 2 groups at mean 2 years postoperatively (range, 2 to 2.3). A power analysis was performed on the number of cases in the cohort.

RESULTS

Postoperative femur-tibia mechanical axis (FTMA) correction was significantly higher in the screw-cement group than in the thick-liner group: 18.8 (±5.6°) versus 15.4 (±5.9°) (P < .01); At mean 2 years after surgery, the American Knee Society Functional Score improvement values were higher in the thick-liner group than in the screw-cement group: 36.3 (±12.4) versus 42.4 (±16.4) (P = .05). Postoperative ISI scores were 0.95 (±0.12) points in the screw-cement group and 0.89 (±0.13) points in the-thick liner group (P = .03). There were no statistically significant differences in the Knee Society Clinical Score, ROM, FJS, stiffness, myasthenia, joint clicking, and revision rate.

CONCLUSION

The results of this study showed no significant difference in clinical outcomes between the 2 reconstruction strategies of the screw cement fill technique and the adequate osteotomy and thick liner technique for Rand IIb tibial plateau defects. However, in patients who have FTMA deformities greater than 20° or in younger patients who need to preserve bone volume, we recommend the screw cement filling technique to ensure stable postoperative results and to prepare these patients for possible later surgery.

Mid-Term Clinical and Radiological Results at a Tertiary Care Hospital in Türkiye: Is Residual Varus Really Important After Mechanically-Aligned Total Knee Arthroplasty?

INTRODUCTION

 Traditionally, in total knee arthroplasty (TKA), it is aimed to keep the mechanical axis of the lower extremity neutral (mechanical alignment: 3° varus-valgus in the coronal plane) to improve long-term outcomes. This study aimed to assess the mid-term radiological and clinical results of patients with postoperative residual varus (more than 3° of varus) after mechanically-aligned TKA.

METHODS

A total of 616 individuals who had undergone TKA for primary knee osteoarthritis between 2008 and 2013 in our tertiary care hospital were retrospectively examined. All TKAs were performed with the mechanical alignment strategy. For radiological evaluation, hip-knee-ankle (HKA) angle, knee alignment angle (KAA), mechanical medial proximal tibial angle (mMPTA), knee inclination (KI), joint line orientation angle relative to ground (JLOA-G), posterior tibial slope (PS), joint line convergence angle (JLCA) were measured. Besides, patients' latest radiographs were screened for any clue of aseptic loosening or mechanical failure. Knee Society Score (KSS) (knee and functional subgroups), and Lysholm, Oxford, and Tegner scores were used for clinical evaluation. In addition, knee flexion and extension limitations were assessed.

RESULTS

After applying the exclusion criteria, a minimum of five-year follow-up result of 110 patients was demonstrated. There were 101 females (92%) and nine males (8%). The mean follow-up time was 65.8 ± 6.3 months (range: 60.8-75.8 years). The mean age was 65.9 ± 7.7 years (range: 39 to 89 years). The preoperative mean mechanical axis angle of the lower extremity was 17.3° ± 7.8° (range: 13.4-43.9°), whereas it was 8.3° ± 3.6° (range: 3.2-19.8°) postoperatively. The preoperative mean flexion angle was 90.7° ± 23.8° (range: 40-130°), and the extension limitation was -2.5° ± 7.4° (range: -40-0°), whereas, postoperatively, they were 102.8° ± 15.4° (range from 40° to 150°) and -3.7° ± 7.5° (range from -40° to 0°), respectively. The latest follow-up's mean KSS knee subgroup was 67 ± 18.4 (range: 12-93), the mean KSS functional subgroup was 74 ± 23.6 (range: 20-100), the mean Lysholm score was 81.7 ± 15.7 (range:25-100), the mean Tegner score was 3.65 ± 0.99 (range: 1-5), the mean Oxford score was 37.4 ± 6.5 (range: 9-48). There was no patient with aseptic loosening or mechanical failure.

CONCLUSIONS

In the mid-term follow-up of patients with residual varus after mechanically-aligned TKA, satisfactory clinical and radiological results were obtained without aseptic loosening or implant failure.

Femoral bowing affects varus femoral alignment but not patient satisfaction in mechanically aligned total knee arthroplasty

PURPOSE

This study evaluated whether patients with particular lower limb morphological factors have femoral and tibial component malpositioning during mechanically aligned total knee arthroplasty (TKA) and lower postoperative satisfaction.

METHODS

This study included 146 knees in 117 Asian patients undergoing TKA for medial osteoarthritis. Preoperative bony morphological factors such as the angle between the femoral mechanical and anatomical axes (MA-AA angle), angle between the anatomical axes of the proximal and distal femur (lateral bowing femoral angle, LBFA), mechanical lateral distal femoral angle, medial proximal tibial angle, and % anatomical axis of the tibia were evaluated, as well as preoperative and 1-year postoperative 2011 Knee Society scores (KSSs).

RESULTS

MA-AA angle and LBFA were significantly larger in knees with varus femoral component alignment versus neutral alignment. Preoperative MA-AA angle was underestimated in patients with larger MA-AA angle or LBFA, especially by inexperienced surgeons. Tibial morphological factors did not affect tibial component alignment. Changes in 2011 KSSs were similar among groups by lower limb alignment or femoral and tibial component alignment.

CONCLUSION

Femoral bowing affects varus femoral component alignment by obscuring preoperative planning, but it had little impact on patient satisfaction when mechanical alignment is targeted during TKA.

Six Commonly Used Postoperative Radiographic Alignment Parameters Do Not Predict Clinical Outcome Scores after Unrestricted Caliper-Verified Kinematically Aligned TKA

Background: Unrestricted caliper-verified kinematically aligned (KA) TKA restores patient’s prearthritic coronal and sagittal alignments, which have a wide range containing outliers that concern the surgeon practicing mechanical alignment (MA). Therefore, knowing which radiographic parameters are associated with dissatisfaction could help a surgeon decide whether to rely on them as criteria for revising an unhappy patient with a primary KA TKA using MA principles. Hence, we determined whether the femoral mechanical angle (FMA), hip–knee–ankle angle (HKAA), tibial mechanical angle (TMA), tibial slope angle (TSA), and the indicators of patellofemoral tracking, including patella tilt angle (PTA) and the lateral undercoverage of the trochlear resection (LUCTR), are associated with clinical outcome scores. Methods: Forty-three patients with a CT scan and skyline radiograph after a KA TKA with PCL retention and medial stabilized design were analyzed. Linear regression determined the strength of the association between the FMA, HKA angle, PTS, PTA, and LUCTR and the forgotten joint score (FJS), Oxford knee score (OKS), and KOOS Jr score obtained at a mean of 23 months. Results: There was no correlation between the FMA (range 2° varus to −10° valgus), HKAA (range 10° varus to −9° valgus), TMA (range 10° varus to −0° valgus), TSA (range 14° posterior to −4° anterior), PTA (range, −10° medial to 14° lateral), and the LUCTR resection (range 2 to 9 mm) and the FJS (median 83), the OKS (median 44), and the KOOS Jr (median 85) (r = 0.000 to 0.079). Conclusions: Surgeons should be cautious about using postoperative FMA, HKAA, TMA, TSA, PTA, and LUCTR values within the present study’s reported ranges to explain success and dissatisfaction after KA TKA.

Varus alignment of the tibial component up to seven degrees is not associated with poor long-term outcomes in a neutrally aligned total knee arthroplasty

PURPOSE

The purpose of this retrospective study was to evaluate the effect of varus alignment of the tibial component on the outcomes with a minimum follow-up of 10 years. The hypothesis was that varus alignment of the tibial component might not affect the outcomes and survival of a neutrally aligned primary TKA.

METHODS

A matched case-control study was designed between 66 patients with varus alignment of the tibial component and 66 with neutral alignment with a minimum follow-up of 10 years. Functional outcome was assessed with the knee surgery scores (KSS) and reduced Western Ontario and MacMaster Universities questionnaire (WOMAC). Patient satisfaction was evaluated by a 0-10 visual analog scale. Radiological evaluation was performed at early postoperative and at final follow-up.

RESULTS

The mean follow-up was 11.9 (SD 2.6) years for both groups. The mean postoperative proximal tibial angle in the varus group was 85.0° (SD 0.9) and 88.8° (SD 0.9) in control group. At the final follow-up, there were no significant differences in KSS, WOMAC, range of motion or patient satisfaction. There were no differences in the coronal anatomical alignment of the TKA between groups. Revision of TKA was performed in four knees in the varus group, and one in control group, due to aseptic loosening of the tibial component in all cases. TKA survival at 10 years was not significantly different between groups.

CONCLUSION

The alignment of the tibial component up to 7° varus did not negatively affect implant survival, patient satisfaction, and function of a well-aligned TKA, with a minimum postoperative follow-up of 10 years.

LEVEL OF EVIDENCE

III.

Mechanical alignment for primary TKA may change both knee phenotype and joint line obliquity without influencing clinical outcomes: a study comparing restored and unrestored joint line obliquity

PURPOSE

In total knee arthroplasty (TKA), knee phenotypes including joint line obliquity are of interest regarding surgical realignment strategies. The hypothesis of this study is that better clinical results, including decreased postoperative knee pain, will be observed for patients with a restored knee phenotype.

METHODS

A retrospective analysis was performed on prospective data, including 1078 primary osteoarthritic knees in 936 patients. The male:female ratio was 780:298, mean age at surgery was 71.3 years ± 8.0. International Knee Society Scores and standardized long-leg radiographs (LLR) were collected preoperatively and at 2 years follow-up after TKA. Patients were categorized using the Coronal Plane Alignment of the Knee (CPAK) classification including the lateral distal femoral angle (LDFA) and medial proximal tibial angle (MPTA) measured on LLR by a single observer, allowing knee phenotypes to be categorized considering the arithmetic hip-knee-ankle (aHKA) angle (MPTA-LDFA) as measure of constitutional alignment, and joint line obliquity (JLO) (MPTA + LDFA). Clinical results were compared between patients with surgically restored preoperative constitutional knee phenotype to patients without restored constitutional knee phenotypes. Descriptive data analysis such as means, standard deviations and ranges were performed. T tests for independent samples were performed to compare group differences. Comparisons of categorical data were performed using the χ² test. Significance was set at p < 0.05.

RESULTS

A third of patients (33.4%) had constitutional knee varus with apex distal JLO. 63.5% of patients had preoperative apex distal JLO. Postoperatively, 57.8% of patients had a neutral HKA (- 2° to 2°) and a neutral JLO (- 3° and 3°), with only 18% of patients with restored constitutional knee phenotype. Of these patients, statistically less postoperative pain was observed in patients where apex distal JLO was restored compared to non-restored apex distal JLO (pain score 46.7 vs. 44.6; p = 0.02) without clinical relevance. Other categories of restored JLO or arithmetic HKA angle were not associated with improved outcomes.

CONCLUSION

This study showed that performing mechanical alignment for primary TKA resulted in most cases in a change of the preoperative knee phenotype. These results emphasize the relevance of considering joint line obliquity to better understand preoperative knee deformity and better restore knee phenotypes with a more personalized realignment strategy to potentially improve TKA postoperative results.

LEVEL OF EVIDENCE

III.

Functional outcomes of residual varus alignment versus mechanical alignment in total knee arthroplasty for varus osteoarthritis: A preferred reporting items for systematic reviews and meta-analyses-compliant meta-analysis

BACKGROUND

One in five patients with mechanical alignment (MA) after total knee arthroplasty (TKA) was reportedly dissatisfied. As constitutional varus knees are common, restoring the patients' natural residual varus (RV) alignment is as an appealing alternative to neutral MA. This meta-analysis aimed to evaluate the effects of RV alignment on the functional outcomes compared with those of MA in TKA for the knees with varus osteoarthritis.

METHODS

The MEDLINE/PubMed, Cochrane Library, and EMBASE databases were comprehensively searched for papers comparing the effects of RV alignment and MA on the functional outcomes from the time of inception of the databases to July 2020. Studies comparing the functional outcomes in the knees subjected to TKA with RV alignment (case group) and MA (control group) were included. The Knee Society knee and functional scores (KSKS and KSFS, respectively), Western Ontario and McMaster University Osteoarthritis Index (WOMAC), Oxford knee score (OKS), and forgotten joint score (FJS) were compared.

RESULTS

Seven studies were finally included; all studies showed a low risk of selection bias and provided detailed demographic data. The pooled mean difference in the KSKS (0.06, 95% confidence interval [CI]: -0.14 to 0.27; p = 0.55) and KSFS (0.08, 95% CI: -0.08 to 0.35; p = 0.56) between RV alignment and MA did not significantly differ. The pooled mean differences in the WOMAC (-0.25, 95% CI: -0.57 to 0.07; p = 0.12), OKS (0.06, 95% CI: -0.15 to 0.27; p = 0.56), and FJS (0.41, 95% CI: -0.18 to 1.00; p = 0.18) between the groups were not significant.

CONCLUSION

The beneficial effects of RV alignment on the functional outcomes are limited compared to those of MA in TKA for varus osteoarthritis to date. Currently, TKA with neutral MA should be considered as the gold standard.

Malposition of components and Femorotibial mechanical Axis changes on pressure distribution in Total knee arthroplasty

BACKGROUND

To the best of our knowledge, no report has analyzed the postoperative results of poor prosthesis position, particularly when the femoral and tibial components are abnormally positioned relative to neutral lower limb alignment. We aimed to investigate pressure distribution in the knee at different lower limb alignments with diverse positions of femoral and tibial components.

METHODS

We established a three-dimensional model of the lower limb using computed tomography and simulated total knee arthroplasty. Tibial and femoral components were changed to 7°, 5°, and 3° of valgus and neutral and 3°, 5°, and 7° of varus positions in the coronal plane. Finite element analysis was performed after applying pressure to simulate weight-bearing, and pressure distribution on the tibial surface was analyzed. We also conducted biomechanical testing using a weight-bearing rig with six cadavers. We measured the pressure at the tibial surface with the position of different components and lower limb alignment.

FINDINGS

Peak pressure on the medial or lateral side of the tibia was determined by the mechanical axis. When tibial components are in 3°,5° and 7° of valgus/varus and femoral components are in 3°,5° and 7° of varus/valgus correspondence, no peak pressure was detected with normal alignment, despite malpositioned components.

INTERPRETATION

Lower limb alignment is more critical than the position of the component. Medial and lateral tibial compartment pressures were evenly distributed if the alignment was neutral. Malpositioned femoral or tibial components changed the femorotibial mechanical axis, and peak pressure of the proximal tibia was positively related to alignment.

Computed Tomography-Based Patient-Specific Instrumentation Loses Accuracy with Significant Varus Preoperative Misalignment

Patient-specific instrumentation (PSI) has been introduced to simplify and make total knee arthroplasty (TKA) surgery more precise, effective, and efficient. We performed this study to determine whether the postoperative coronal alignment is related to preoperative deformity when computed tomography (CT)-based PSI is used for TKA surgery, and how the PSI approach compares with deformity correction obtained with conventional instrumentation. We analyzed pre- and post-operative full length standing hip-knee-ankle (HKA) X-rays of the lower limb in both groups using a convention > 180 degrees for valgus alignment and < 180 degrees for varus alignment. For the PSI group, the mean (± SD) pre-operative HKA angle was 172.09 degrees varus (± 6.69 degrees) with a maximum varus alignment of 21.5 degrees (HKA 158.5) and a maximum valgus alignment of 14.0 degrees. The mean post-operative HKA was 179.43 degrees varus (± 2.32 degrees) with a maximum varus alignment of seven degrees and a maximum valgus alignment of six degrees. There has been a weak correlation among the values of the pre- and post-operative HKA angle. The adjusted odds ratio (aOR) of postoperative alignment outside the range of 180 ± 3 degrees was significantly higher with a preoperative varus misalignment of 15 degrees or more (aOR: 4.18; 95% confidence interval: 1.35-12.96; p = 0.013). In the control group (conventional instrumentation), this loss of accuracy occurs with preoperative misalignment of 10 degrees. Preoperative misalignment below 15 degrees appears to present minimal influence on postoperative alignment when a CT-based PSI system is used. The CT-based PSI tends to lose accuracy with preoperative varus misalignment over 15 degrees.

Functional Alignment Philosophy in Total Knee Arthroplasty – Rationale and technique for the varus morphotype using a CT based robotic platform and individualized planning

Introduction: Alignment techniques in total knee arthroplasty (TKA) continue to evolve. Functional alignment (FA) is a novel technique that utilizes robotic tools to deliver TKA with the aim of respecting individual anatomical variations. The purpose of this paper is to describe the rationale and technique of FA in the varus morphotype with the use of a robotic platform. Rationale: FA reproduces constitutional knee anatomy within quantifiable target ranges. The principles are founded on a comprehensive assessment and understanding of individual anatomical variations with the aim of delivering personalized TKA. The principles are functional pre-operative planning, reconstitution of native coronal alignment, restoration of dynamic sagittal alignment within 5° of neutral, maintenance of joint-line-obliquity and height, implant sizing to match anatomy and a joint that is balanced in flexion and extension through manipulation of implant positioning rather than soft tissue releases. Technique: An individualized plan is created from pre-operative imaging. Next, a reproducible and quantifiable method of soft tissue laxity assessment is performed in extension and flexion that accounts for individual variation in soft tissue laxity. A dynamic virtual 3D model of the joint and implant position that can be manipulated in all three planes is modified to achieve target gap measurements while maintaining the joint line phenotype and a final limb position within a defined coronal and sagittal range. Conclusion: Functional alignment is a novel knee arthroplasty technique that aims to restore constitutional bony alignment and balance the laxity of the soft tissues by placing and sizing implants in a manner that it respects the variations in individual anatomy. This paper presents the approach for the varus morphotype.

Residual varus alignment can reduce joint awareness, restore joint parallelism, and preserve the soft tissue envelope during total knee arthroplasty for varus osteoarthritis

PURPOSE

The objectives were to compare the coronal joint configuration of the knee joints, coronal gap imbalances requiring substantial medial release, and patient-reported outcomes, including the forgotten joint score, between knees in which residual varus alignment was intentionally allowed according to an individualised lower limb analysis and those with mechanical alignment in total knee arthroplasty for varus osteoarthritis.

METHODS

Consecutive primary navigated total knee arthroplasty procedures for varus osteoarthritis were retrospectively reviewed. The study cohort was stratified based on whether residual varus alignment was intentionally allowed. Propensity-score matching was performed based on the baseline characteristics, including demographic characteristics, preoperative radiological measurements, and the Western Ontario and McMaster University Osteoarthritis Index (mechanical alignment group vs residual varus group). The patient-reported outcomes and coronal joint line orientation of the knee (relative to the ground) and ankle were evaluated. Coronal gap differences and coronal gap imbalances were analysed using intraoperative gap measurements.

RESULTS

Relative to the ground and ankle, the postoperative knee joint line orientation slanted down laterally in the mechanical alignment group (- 3.05˚ ± 1.62, relative to the ground; - 2.65˚ ± 1.56, relative to the ankle joint), but was parallel in the residual varus group (- 0.75˚ ± 1.59, relative to the ground; - 0.95˚ ± 1.71, relative to the ankle joint). Coronal gap differences at extension and the proportion of coronal gap imbalances requiring substantial medial release were 1.27 ± 1.53 and 6% in the residual varus group and 2.32 ± 1.24 and 15% in the mechanical alignment group. Postoperatively, the residual varus group showed higher Western Ontario and McMaster University Osteoarthritis Index scores and total forgotten joint scores than the mechanical alignment group (6.97 ± 4.75 vs. 10.31 ± 5.74 and 56.42 ± 12.85 vs. 45.69 ± 14.49, respectively).

CONCLUSION

Intentionally allowed residual varus alignment with individualised analysis of lower limb alignment restored the parallel joint line of the knees, preserved the soft tissue envelope, and reduced joint awareness after total knee arthroplasty for varus osteoarthritis.

LEVEL OF EVIDENCE

Therapeutic, Level III retrospective case-control study.

Correctability of the knee joint observed under a stressed state

BACKGROUND

Well-balanced postoperative knee joints are often based on subjective 'feel' of experienced surgeons rather than quantifiable references. Most alignment strategies continue to reference the bone despite the complexity in anatomical variations and presence of deformity. Categorical prescription of a singular alignment philosophy for all patients may not be appropriate. This study aims to characterize coronal alignment correctability in relation to anatomical measures to develop a mechanism for distinguishing patients for whom repeatable strategies are optimal in the form of alternative alignment techniques or advanced soft tissue balancing.

METHODS

A consecutive series of 103 pre-operative knees who underwent primary total knee arthroplasty (TKA) were analysed. Pre-operative supine computer tomography (CT) scans were segmented, with output STL bone models placed against several stressed positions determined by the TELOS SD-900 (METAX, Germany) device. Anatomical analysis using two-dimensional (2D) -3D image registration was performed. Statistical analysis was conducted for variations in anatomical morphology and regression modelling was used to determine the relationship between these measurements and correctability of a patient.

RESULTS

The mean preoperative supine hip-knee-ankle (HKA) angle was 5.1° and 2.3°, lateral distal femoral angle (LDFA) was 2.0° and 3.1°, medial proximal tibial angle (MPTA) was 3.7° and 3.0° varus for male and female, respectively. The mean laxity range was 4.3°. We found 36% of valgus patients and 55% of mild varus patients to be correctable. Supine HKA was a statistically significant predictor for correctability (P < 0.001). A statistically significant correlation between laxity and the HKA (P = 0.01) as well as LDFA angles (P = 0.01) exist for the mild varus cohort.

CONCLUSION

Relationship between HKA angle and the correctability of the knee joint to neutral in patients presenting with mild to moderate varus cannot be consistently predicted using bony anatomy. If there is a desire to avoid ligament release during TKA, careful consideration of both a patient's bony anatomy and soft tissue laxity envelope must be made prior to surgery.

Comparison of Outcomes After Total Knee Arthroplasty Involving Postoperative Neutral or Residual Mild Varus Alignment: A Systematic Review and Meta-analysis

Comparing mainly clinical and functional outcomes as well as prosthesis survival with neutral and residual mild varus alignment, we searched PubMed, Embase, Cochrane Library and Web of Science databases from 1 January 1974 to 18 December 2020 to identify studies comparing clinical and functional outcomes as well as prosthesis survival in the presence of different alignments after total knee arthroplasty (TKA) for varus knees. The included studies were assessed by two researchers according to the Newcastle–Ottawa Scale (NOS). Postoperative neutral alignment (0° ± 3°) was compared to residual mild varus (3°–6°) and residual severe varus (>6°). Meta‐analysis was performed using Review Manager 5.3. The odds ratios (OR) and mean differences (MD) were used to compare dichotomous and continuous variables. The fixed‐effect model and random‐effect model were used to meta‐analyze the data. Nine studies were included in the meta‐analysis with 1410 cases of postoperative neutral alignment, 564 of residual mild varus alignment and 175 of residual severe varus alignment following TKA, all of which were published after 2013. Three studies scored 7 points on the NOS, while the remaining studies scored 8 points, suggesting high quality. The pooled mean differences (MDs) of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score were 1.07 [95% confidence interval (CI) −1.06 to 3.20; P = 0.32; I² = 79%]. The meta‐analysis showed that neutral alignment and mild varus alignment were associated with similar the Oxford Knee Score (OKS), Knee Society Knee Score (KS‐KS), and Knee Society Function Score (KS‐FS), while neutral alignment was associated with lower Forgotten Joint Score (FJS) [mean difference −6.0, 95% confidence interval (CI) −9.37 to −2.64, P = 0.0005]. Neutral alignment was associated with higher KS‐KS than severe alignment (M 2.98, 95% CI 1.42 to 4.55, P = 0.0002; I² = 0%) as well as higher KS‐FS (M 8.20, 95% CI 4.58 to 11.82, P < 0.00001; I² = 0%). Neutral alignment was associated with similar rate of survival as mild varus alignment (95% CI 0.36 to 9.10; P = 0.48; I² = 65%) or severe varus alignment (95% CI 0.94 to 37.90; P = 0.06; I² = 61%). There was no statistical difference in others. Residual mild varus alignment after TKA may lead to similar or superior outcomes than neutral alignment in patients with preoperative varus knees, yet the available evidence appears to be insufficient to replace the current gold standard of neutral alignment. Severe varus alignment should be avoided.

Degree of coronal alignment correction can't predict knee function in total knee replacement

BACKGROUND

Whether neutral alignment brings better clinical outcomes is controversial. Consideration of the preoperative knee condition of patients and some limitations of previous studies, we suggested that other index may be more important than a generic target of 0° ± 3° of a neutral axis to reflect changes in coronal alignment after total knee replacement (TKR). The purpose of this study was to explore the relationship between alignment and functional outcome with a new grouping method and the concept of correction rate.

METHODS

The study included 358 knees, the mean follow-up period was 3.62 years. A new grouping method was adopted to divide patients into three groups based on the degree of correction of mechanical femoral-tibial angle (MFTA): under-correction (n = 128), neutral (n = 209) and over-correction (n = 21). Hospital for Special Surgery (HSS) score were compared among the 3 groups (ANOVA with or without LSD t-test). In addition, we also attempt to further explore whether the concept of correction rate can predict postoperative functional score (Simple linear correlation analysis).

RESULTS

HSS score showed significant improvement in all groups. There was no difference in HSS score (88.27 vs 88 vs 85.62) (p = 0.88) or incremental scores (26.23 vs 25.22 vs 22.88) (p = 0.25) based on the postoperative alignment category for the degree of correction of MFTA at the last follow-up. The correlational analyses also didn't show any positive results (r = -0.01 p = 0.95, r = -0.01 p = 0.97, r = 0.11 p = 0.15, r = 0.01 p = 0.90).

CONCLUSION

Categorization of optimal coronal alignment after TKR may be impractical. But we still believe that the concept of correction rate and new grouping method are worthy of research which can reflects the preoperative knee condition and the change of coronal alignment. Perhaps it can be better used in TKR in the future.

LEVEL OF EVIDENCE

III.

Preoperative and intraoperative factors contributing to patient satisfaction after bi-cruciate stabilized total knee arthroplasty

BACKGROUND

One of the causes of dissatisfaction following total knee arthroplasty (TKA) is abnormal knee kinematics. A newly designed bi-cruciate stabilized (BCS) TKA system has been developed to produce close-to-normal kinematics because of its anatomic tibiofemoral articular geometry and cam-post mechanism. Although BCS TKA is expected to improve patient satisfaction, no reports have described the appropriate technique or soft tissue handling required to achieve excellent satisfaction with BCS TKA. This study is to identify preoperative and intraoperative predictors of patient satisfaction after BCS TKA.

METHODS

Altogether, we studied 113 knees with primary varus knee osteoarthritis that underwent BCS TKA with a navigation system. Preoperative parameters including Knee Society Score and patient-reported scores [the Knee injury and Osteoarthritis Outcome Score (KOOS)] and intraoperative parameters including coronal, sagittal and axial alignment and joint laxity in each compartment that affected patient satisfaction was evaluated. Satisfaction score was evaluated with use of the 2011 Knee Society Scoring system. The multivariate regression analysis included age and preoperative and intraoperative parameters that correlated with satisfaction scores in the univariate analysis (P < 0.05).

RESULTS

The mean satisfaction score was 28.2 ± 6.1. Multivariate regression analysis showed that the predictors of patient satisfaction were a preoperative high KOOS score for activities of daily living (P < 0.001), male sex (P = 0.005), older age (P = 0.027), and minimal medial joint laxity during flexion (P = 0.031).

CONCLUSION

When performing BCS TKA, surgeons should pay attention to maintaining proper stability of the medial compartment, especially during flexion.

[Optimal lower limb alignment and soft tissue balancing strategy for robot-assisted total knee arthroplasty]

Lower limb alignment and soft tissue balance are important factors affecting patient satisfaction, clinical functional outcome, and prosthetic long-term survival rate after total knee arthroplasty (TKA). Robot-assisted TKA (rTKA) has the advantages of achieving precise osteotomy and soft tissue balance. However, rTKA under the guidance of classic mechanical alignment principles does not significantly improve the functional outcome after operation. The new TKA alignment principles, such as kinematic alignment (KA) and functional alignment (FA), can better consider the patient's own knee joint morphology and kinematic characteristics, which may help improve the clinical results of TKA. With the help of more objective and accurate soft tissue balance assessment tool such as pressure sensors, KA and FA have been proven to better achieve soft tissue balance. rTKA can achieve non-neutral alignment goals such as KA or FA more accurately and reproducibly. The use of these lower limb alignment and soft tissue balancing strategies will be expected to further increase the patients' satisfaction rate after rTKA.

Targeted treatment for osteoarthritis: drugs and delivery system

The management of osteoarthritis (OA) is a clinical challenge due to the particular avascular, dense, and occluded tissue structure. Despite numerous clinical reports and animal studies, the pathogenesis and progression of OA are still not fully understood. On the basis of traditional drugs, a large number of new drugs have been continuously developed. Intra-articular (IA) administration for OA hastens the development of targeted drug delivery systems (DDS). OA drugs modification and the synthesis of bioadaptive carriers contribute to a qualitative leap in the efficacy of IA treatment. Nanoparticles (NPs) are demonstrated credible improvement of drug penetration and retention in OA. Targeted nanomaterial delivery systems show the prominent biocompatibility and drug loading-release ability. This article reviews different drugs and nanomaterial delivery systems for IA treatment of OA, in an attempt to resolve the inconsonance between in vitro and in vivo release, and explore more interactions between drugs and nanocarriers, so as to open up new horizons for the treatment of OA.

Influence of surgical factors on patient satisfaction after bi-cruciate stabilized total knee arthroplasty: retrospective examination using multiple regression analysis

Background

One of the causes of dissatisfaction following total knee arthroplasty (TKA) is abnormal knee kinematics. A newly designed bi-cruciate stabilized (BCS) TKA system has been developed to produce close-to-normal kinematics because of its anatomic tibiofemoral articular geometry and cam-post mechanism. Although BCS TKA is expected to improve patient satisfaction, no reports have described the appropriate technique or soft tissue handling required to achieve excellent satisfaction with BCS TKA. This study is to identify intraoperative surgical predictors of patient satisfaction after BCS TKA.

Methods

We studied 104 knees with primary varus knee osteoarthritis that underwent BCS TKA with a navigation system retrospectively. Surgical parameters including coronal, sagittal and axial alignment and joint laxity in each compartment that affected patient satisfaction was evaluated. Satisfaction score was evaluated with use of the 2011 Knee Society Scoring system. The multivariate regression analysis included age, gender, body mass index and intraoperative parameters that correlated with satisfaction scores in the univariate analysis (P < 0.05). The current study focused on the patient satisfaction score at 1 year postoperatively and didn’t evaluate the long term clinical results nor survivorship.

Results

The postoperative satisfaction score was 28.6 ± 8.1. Multivariate analysis showed that medial joint laxity at 30° flexion (P = 0.003), tibial excessive external rotation alignment (P = 0,009) and tibial varus alignment (P = 0.029) were predictors of poor satisfaction score.

Conclusions

When performing BCS TKA, surgeons should pay attention to maintaining proper stability of the medial compartment at mid flexion range and should avoid tibial varus and excessive external rotational alignment.

Association of HSS score and mechanical alignment after primary TKA of patients suffering from constitutional varus knee that caused by combined deformities: a retrospective study

For pre-operative osteoarthritis (OA) patients with varus knee, previous studies showed inconsistent results. Therefore, we conducted this study to better identify the association of Hospital for Special Surgery (HSS) score and mechanical alignment. 44 patients (51 knees) with constitutional varus knee caused by combined deformities (LDFA (lateral distal femoral angle) > 90°and MPTA (medial proximal tibial angle) < 85°)) were selected and analyzed with a mean follow-up period of 14 months after total knee arthroplasty (TKA). From January 2015 to December 2016, patients were collected consecutively after primary TKA. After filtering, fifty-one knees (44patients) were analyzed with a mean follow-up period of 14 months. All patients were divided into two groups based on post-operative hip-knee-ankle (HKA) acute angle: varus mechanical alignment (VMA) group (HKA < - 3°) and neutral mechanical axis (NMA) group (- 3° ≤ HKA ≤ 3°). 30 knees were included in the NMA group, and 21 knees in the VMA group. Comparisons of HSS between NMA group and VMA group were performed. After adjusting for age and Body Mass Index (BMI) confounders, Compared with NMA group, the HSS score in VMA group decreased by 0.81 units (95% CI, - 3.37 to 1.75) p = 0.5370). For pre-operative constitutional varus knee caused by combined deformities in chinese populations, no significant association between post-operative lower limb mechanical alignment and HSS score was found.

Varus deformity in the proximal tibia and immediate postoperative varus alignment result in varus progression in limb alignment in the long term after total knee arthroplasty

PURPOSE

The aim of this study was to examine and evaluate the factors associated with changes in limb alignment 10 years after total knee arthroplasty (TKA). The hypothesis was that bone morphology and immediate postoperative alignment could be correlated with long-term post-operative alignment changes following TKA.

METHODS

This study retrospectively analysed 136 consecutive primary TKA cases for varus deformity, performed from 2006 to 2008, that could be followed for at least 10 years postoperatively. Anteroposterior long-leg weight-bearing radiographs were obtained within 1 month and at least 10 years after surgery. The hip-knee-ankle (HKA) angle immediately after surgery was compared with that 10 years later; factors correlating with the change in HKA angle (δHKA) were evaluated.

RESULTS

The mean HKA angles were significantly different between immediate and long-term postoperative assessments (0.1° ± 1.9° vs. 1.2° ± 2.9°, p < 0.001). Furthermore, a significant difference was observed in the outlier ratio (> 3° deviation from the 0° of HKA angle) (10% vs. 24%, p = 0.002). δHKA strongly correlated with a higher preoperative tibial plateau tip-to-proximal tibial shaft (TPTPS) angle, higher postoperative HKA angle, lateral distal femoral angle, and lower postoperative medial proximal tibial angle.

CONCLUSION

Varus deformity in the proximal part of the tibia, immediate postoperative varus alignment, and varus position of the femoral and tibial components may lead to varus progression in limb alignment in the long term, even 10 years after TKA; the surgeon should, therefore, weigh the risks of leaving a varus alignment during surgery. Moreover, if the preoperative TPTPS angle is high, the alignment may become varus after TKA, even in patients who have acquired neutral alignment.

LEVEL OF EVIDENCE

IV.

Varus alignment after total knee arthroplasty results in greater axial rotation during deep knee bend activity

BACKGROUNDS

The correlation between in vivo knee kinematics and alignment has not been fully elucidated. Recently, similar or better clinical outcomes have been reported by restoration of mild varus alignment after total knee arthroplasty for preoperative varus knees. The aim of this study was to evaluate the effect of postoperative alignment on knee kinematics during a deep knee bend activity.

METHODS

In vivo knee kinematics of 36 knees (25 patients) implanted with tri-condylar total knee arthroplasty were analyzed with a three dimensional model fitting approach using fluoroscopy. Under fluoroscopic surveillance, individual video frames were digitized at 30° increments from full extension to maximum flexion. Postoperative coronal and sagittal alignments were assessed using radiographs, and rotational alignment was assessed with computed tomography. Pearson correlation coefficients were calculated to determine the correlations between the alignment data and kinematic factors.

FINDINGS

Correlation analysis showed that coronal alignment was significantly correlated with knee kinematics. The varus alignment of the limb and tibial component led to a greater axial rotation from full extension to maximum flexion and more rotated position in the mid to deep flexion range. Neither the rotational alignment of the femoral nor tibial components showed significant correlation with axial rotation from full extension to maximum flexion.

INTERPRETATION

Varus alignment resulted in greater axial rotation, which could represent near-normal knee kinematics. The current study can be a kinematic rationale reporting similar or better clinical and functional outcomes for the total knee arthroplasty with residual varus alignment.

Current evidence base for kinematic alignment

BACKGROUND

Kinematic alignment recently became an alternative alignment option for total knee arthroplasty (TKA). Beside previous studies assessing mechanical alignment in comparison to unintentional malalignment of TKA in terms of implant survival and clinical outcome, more and more studies have focused on the direct comparison of intentional kinematic alignment with mechanical alignment of the prosthesis. In the past 5 years the number of studies with respect to kinematic alignment has risen from 11 to 91 studies.

AIM

The aim of this review article is to give a narrative overview of the current literature in the debate concerning kinematic and mechanical alignment in TKA.

Dynamic deformation of femur during medial compartment knee osteoarthritis

OBJECTIVES

The aim of this study was to evaluate the morphological changes of the femur in the coronal plane in progressing varus gonarthrosis and to explore the interrelation of each component.

PATIENTS AND METHODS

From January to July 2017, radiographic images of 1538 knees of 883 consecutive patients were collected and analyzed. We drew the alignments and measured the orientation angles of the lower extremities and compared the results among age groups for each sex. Correlation and regression tests were used to analyze the measurements.

RESULTS

There were significant differences in the neck-shaft angle (NSA), femoral bowing angle (FBA) and anatomic medial distal femoral angle (aMDFA) by age group in females, whereas the differences were not significant in males. In females, a positive correlation was found between age and the FBA and aMDFA (r = 0.253, 0.141, p<0.01), and a negative correlation was found between age and the NSA while the FBA was controlled (r = -0.065, p<0.05). The FBA was positively correlated with the NSA (r = 0.312, p<0.01) and aMDFA (r = 0.233, p<0.01). The NSA, FBA, and aMDFA together affected 72.2% of the mechanical medial distal femoral angle (mMDFA) (β = 0.071, -0.528, 0.803, p<0.01).

CONCLUSION

As knee osteoarthritis (KOA) progressed, dynamic deformation of the femur was found in females, while no obvious changes were found in males. Femoral mechanical axis varus (mMDFA decrease) was the result of changes in the NSA, FBA and aMDFA. The deformation was throughout the femur rather than in a local area, as femur bowing can lead to corresponding changes in both ends of the femur. We provided a theoretical basis for TKA and knee-salvage treatment, and more attention should be paid to aging patients, especially females, in the preoperative protocol for orthomorphia.

Impact of preoperative varus deformity on postoperative mechanical alignment and long-term results of "mechanical" aligned total knee arthroplasty

PURPOSE

Preoperative varus deformity may affect postoperative mechanical alignment and outcomes of total knee arthroplasty (TKA). In this study, we aimed to determine whether (1) greater degrees of preoperative varus deformity increase the incidence of varus-aligned TKAs and (2) residual varus alignment improves the long-term survival rate in TKAs with preoperative varus deformity.

METHODS

We retrospectively reviewed 905 primary TKAs for varus-type osteoarthritis from November 1998 to June 2009. The mean follow-up was 8.23 years (±3.47 years). We measured pre- and postoperative mechanical hip-knee-ankle axis angle (HKA) on full-length standing radiographs to assess the severity of preoperative varus deformities, defined as mild (0°<HKA≤5°), moderate (5°<HKA≤10°), severe (10°<HKA≤15°), and very severe (HKA>15°). Postoperative alignment was divided to four groups: valgus (HKA<-3°), neutral (-3°≤HKA≤3°), mild varus (3°<HKA≤6°), and severe varus (HKA>6°). We performed survival analysis in all cases for mechanical failure.

RESULTS

Varus-aligned TKAs increased proportionally to increasing preoperative varus deformity (p<0.001). The survival rate showed no significant difference according to the preoperative varus deformity (p=0.147). However, the survival time for postoperative neutral alignment (16.13±0.10 years, 95% CI 15.94-16.33 years) was longer than the survival time for mild varus (15.32±0.35 years, 95% CI 14.64-16.00 years) and severe varus (13.38±0.53 years, 95% CI 12.35-14.42 years) alignment (p<0.001).

CONCLUSION

Postoperative varus malalignment appears to increase proportionally to the severity of preoperative varus deformity. Also, postoperative neutral alignment results in longer TKA survival time than residual varus alignment.

LEVEL OF EVIDENCE

III, Retrospective comparative cohort study.

Influence of limb alignment and prosthetic orientation on patient-reported clinical outcomes in total knee arthroplasty

BACKGROUND

The relationship between postoperative limb alignment and clinical outcomes in primary total knee arthroplasty (TKA) is well reported, but the instruments used to evaluate clinical outcomes of TKA are mainly scoring systems from the physician's viewpoint, not patient-reported outcomes. The purpose of this study was to investigate retrospectively the relationship between postoperative limb alignment and patient-reported clinical outcomes using the 2011 Knee Society Knee Scoring System (2011 KSS).

METHODS

The present study included 155 knees of patients (median age, 74 years) who underwent primary TKA for varus osteoarthritis, with a mean follow-up period of 46 months. The subjects were divided into three groups based on postoperative limb alignment and femoral and tibial component positioning angle (varus, neutral, and valgus). The 2011 KSS scores were compared among the groups.

RESULTS

For limb alignment, the postoperative objective knee indicator score was significantly lower in the valgus group than in the varus and neutral groups, whereas no significant differences were observed in any subjective categories of the 2011 KSS. However, for the femoral component angle, functional activity scores were significantly lower in the valgus group than in the varus and neutral groups.

CONCLUSIONS

The subjective patient-reported score was not affected by the postoperative limb alignment. However, the valgus femoral component angle resulted in lower subjective functional scores. For clinical relevance, postoperative valgus positioning of femoral component should be avoided from patient-reported functional aspects during TKA.

Patient-specific instrumentation in total knee arthroplasty

INTRODUCTION

Total knee arthroplasty (TKA) is one of the most commonly performed orthopedic procedures. During the past decade, patient-specific instrumentation (PSI) has been commercially introduced in order to simplify and make TKA surgery more effective, precise and efficient than conventional mechanical instrumentation (CI) and computer-assisted surgery (CAS). Nevertheless, there are critical arguments against PSI for routine use. The aim of the current manuscript is to describe advantages and limitations of PSI for primary TKA.

AREAS COVERED

By means of a description of the available literature different aspects are discussed (accuracy, clinical and functional outcomes, operative time, blood loss, efficiency and costs).

EXPERT OPINION

Most publications do not claim a significant increase in PSI accuracy over CI, but they also do not postulate PSIs accuracy is worse either. Regarding clinical aspects, PSI did not appear to give any advantage over standard techniques although, equally, it did not appear to show any disadvantages. PSI seems to reduce operative time, could reduce perioperative blood loss and provides logistical benefits in the operation room. Further studies will be required to more thoroughly assess all the advantages and disadvantages of this promising technology as an alternative to CI and CAS.

Over-voluming predicted by pre-operative planning in 24% of total knee arthroplasty

PURPOSE

Numerous studies demonstrated that prosthetic overhang and over-sizing cause pain and stiffness following total knee arthroplasty (TKA), but none considered volume changes within the joint capsule. This study was designed to investigate differences in volumes of resected bone compared to implanted components in TKA, and to determine the incidence and factors related to 'over-voluming'.

METHODS

Three-dimensional reconstructions were created from 100 magnetic resonance imaging scans taken to design patient-specific instruments for TKA. The preoperative simulations were used to calculate the volume ratio (VR) by dividing volume of planned components by that of planned bone resections. Uni- and multi-variable linear regressions were performed to determine associations between 'over-voluming' (VR > 1.0) and gender, implant size and version (standard versus narrow), osteophytes, resection levels, external rotation of the femoral component, hip-knee-ankle (HKA) angle, mechanical lateral distal femoral angle (mLDFA), and mechanical medial proximal tibial angle (mMPTA).

RESULTS

The overall implant/bone volume ratio was 0.91 ± 0.11 (range 0.63-1.16) with 'over-voluming' observed in 24 knees. Multi-variable regression confirmed over-voluming to be associated with lower mLDFA (OR 0.66; CI 0.45-0.93; p = 0.026) and extensive osteophytes (OR 0.14; CI 0.03-0.61; p = 0.014), but not HKA angle (OR 0.98; CI 0.76-1.26; p = n.s.).

CONCLUSIONS

Over-voluming was observed in 24% of knees, in which the implant volume exceeded the resected volume by up to 16%. Over-voluming was associated with intra-articular femoral valgus (low mLDFA), but not directly associated with tibial deformity (mMPTA) or HKA angle. Over-voluming could be associated with prosthetic overhang or excessive tensions within the joint capsule, and, therefore, contribute to unexplained pain and stiffness following TKA.

LEVEL OF EVIDENCE

IV, Retrospective cohort study.

Navigation-Assisted Total Knee Arthroplasty for a Valgus Knee Improves Limb and Femoral Component Alignment

The purpose of this study was to evaluate the influence of navigation-assisted surgery on radiographic and clinical outcomes after total knee arthroplasty (TKA) for a valgus knee. The authors identified all patients who underwent TKA for a valgus knee between January 2005 and December 2015. Among 83 conventional TKA cases and 55 navigation-assisted TKA cases, propensity score matching was performed for age, sex, body mass index, and preoperative lower limb mechanical axis. Fifty knees were matched to 50 knees. Each case was evaluated regarding lower limb mechanical axis, mechanical lateral distal femoral angle, medial proximal tibial angle, patellar tilt angle, Western Ontario and McMaster Universities Osteoarthritis Index, Knee Society score, and range of motion. Lower outliers of lower limb mechanical axis (30% vs 8%, P=.008) and mechanical lateral distal femoral angle (24% vs 10%, P=.046) were found in navigation-assisted TKA. However, outliers of medial proximal tibial angle, Western Ontario and McMaster Universities Osteoarthritis Index, Knee Society score, and range of motion were similar between the 2 different surgical techniques. Navigation-assisted surgery is correlated with fewer outliers of postoperative lower limb alignment and femoral component position but not tibial component position in TKA for preoperative valgus knee. Clinical outcomes for navigation-assisted TKA were not superior to those for conventional TKA. [Orthopedics. 2019; 42(2):e253-e259.].

The value of postoperative prosthesis alignment and patellar height measurements on standard X-rays after Total Knee Arthroplasty: Does it relate to knee function after 5 years?

BACKGROUND

The purpose of this retrospective cohort study was to investigate the influence of parameters of malalignment on knee function 5 years post TKA and, additionally, to explore alterations in patellar height after TKA.

METHODS

All 661 patients undergoing TKA between 2010 and 2011 were considered for inclusion. Preoperative and 1-year postoperative short-leg radiographs were assessed for malalignment parameters: coronal tibial angle (cTA), sagittal tibial angle (sTA), femoral flexion angle (FFA) and mediolateral tibial mismatch. Patellar height was measured using the modified Insall-Salvati ratio. We determined improvements in knee function utilizing the Knee Society Score (Function score, KSS-F), Oxford Knee Score (OKS) and Algofunctional index (AI). Influences of malalignment parameters were analyzed univariate and selected (p < 0.10) for multivariate linear regression analysis. Inter-observer reproducibility was assessed by test-retest analysis of 30 randomly selected radiographs and calculation of an intra-class correlation coefficient (ICC) for all radiographic parameters.

RESULTS

Three-hundred and four patients were included. Multivariate regression showed degrees of cTA malalignment to be significantly associated with only the KSS-F (β = -3.52). Correction of coronal deformity was stronger associated with knee function (KSS-F β = 2.81; AI β = -0.36). Patellar height was significantly reduced after TKA (1.51 vs 1.44). Decrease of patellar height was weakly associated with the OKS (β = 10.69). ICC scores were: cTA 0.81, sTA 0.57, IS 0.72, FFA 0.75.

CONCLUSION

Postoperative coronal tibial plate alignment and correction of preoperative coronal deformity are associated with improved knee function 5 years post TKA. Decrease in patellar height was weakly associated with knee function. Short-leg radiography can be a sufficient screening tool for prosthesis alignment.

The impact of residual varus alignment following total knee arthroplasty on patient outcome scores in a constitutional varus population

BACKGROUND

Following a total knee arthroplasty (TKA), restoration of the mechanical axis of the lower limb to a neutral position of 0° ± 3° is generally considered the standard of care. Little is known, however, regarding the impact of realignment defined according to the patient's physiologic anatomy on clinical outcome scores.

METHODS

The study included 67 knees with a mean age of 65.9 ± 8.3 years with unilateral osteoarthritis (OA) who underwent a primary unilateral TKA for medial end-stage OA. Patients were categorized based on post-operative limb alignment in one of two ways, either based on alignment relative to their contralateral, physiologic side (physiologic), or alignment relative to a neutral axis (neutral). Knee Society Score (KSS), Western Ontario & McMaster Universities Osteoarthritis Index (WOMAC), and the 12-Item Short Form Survey (SF-12) were compared between the two groups.

RESULTS

WOMAC Total and subscale scores improved for both groups between the pre- and post-operative time points. SF-12 scores were comparable post-operatively between the groups. WOMAC and KSS total and subscale scores were slightly greater post-operatively in the group not aligned according to their physiologic anatomy (neutral). However, none of these differences reached a level of significance.

CONCLUSION

Post-operatively, residual varus and neutral limb alignment lead to comparable clinical outcome scores. In a constitutional varus population with medial end-stage OA, aligning the lower limb during a TKA to a neutral position rather than the patient's native anatomy does not negatively impact self-reported patient outcome scores at the one and two-year time points.

Does the Preoperative Varus Deformity Influence the Survival of Postoperative Neutral-Aligned TKAs? An Analysis With a Minimum 5-Year Follow-Up

BACKGROUND

Postoperative neutral alignment may be an important factor for longevity of total knee arthroplasty (TKA). In knees with severe varus deformity, greater soft tissue release and bone resection were required to achieve neutral alignment. We investigated the relationship between the severity of preoperative varus deformity and longevity of neutral-aligned TKAs.

METHODS

Of the 723 knees in patients who underwent primary TKA for varus-type osteoarthritis between November 1998 and June 2009, 496 knees aligned neutrally (the postoperative mechanical hip-knee-ankle [HKA] axis angle ranged between -3° and 3°) and followed up for at least 5 years were included in the study. The mean follow-up period was 9.28 years. Patients were divided into 4 groups based on their preoperative HKAs: mild (0° < HKA ≤ 5°, n = 79), moderate (5° < HKA ≤ 10°, n = 204), severe (10° < HKA ≤ 15°, n = 149), and very severe (HKA > 15°, n = 64) groups. Failure was defined as need for revisional TKA for mechanical reason. Survival was analyzed by Kaplan-Meier method and log-rank test.

RESULTS

The overall failure rate was 2.02% (10 of 496 prostheses). The cumulative survival rates of neutral-aligned TKAs at 10 years were 97.4% (95% confidence interval [CI], 93.9%-100%), 99.0% (95% CI, 97.6%-100%), 97.8% (95% CI, 95.4%-100%), and 96.9% (95% CI, 92.6%-100%) in mild, moderate, severe, and very severe varus groups, respectively. There were no significant differences between group survival rates (P = .395).

CONCLUSION

The severity of preoperative varus deformity did not affect survival rates of neutral-aligned TKAs over 10 years.

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.