Coronal Femoral Component Angle Research Articles

Favorable early outcomes of medial unicompartimental knee arthroplasty in active patients presenting a degenerative medial meniscus root tear with meniscal extrusion and mild radiographic osteoarthritis.

There is only limited literature available evaluating the preferable treatment for active mid-age or elderly patients presenting with a degenerative medial meniscus root tear (d-MMRT) with medial meniscal extrusion (MME) and early-phase radiographic osteoarthritis (OA), failing to provide solid evidence. The aim of this study was to evaluate early outcomes of medial unicompartimental arthroplasty (mUKA) in active patients presenting a d-MMRT with meniscal extrusion and mild radiographic OA of the knee. To prove this claim we hypothesized that (1) patients with a d-MMRT with initial grade 1-3 KL OA of the medial compartment of the knee present the same pre-operative symptoms as patients with an end-stage grade 4 K-L OA, and that (2) those patients with d-MMRT and low-grade OA achieve the same early clinical and functional outcomes when treated with mUKA compared to patients with end-stage medial OA. We reviewed the prospectively collected data of 185 patients undergoing robotic-assisted image-based mUKA from January 2021 to July 2022 at a single Institution. We identified two different cohorts of non-consecutive patients: a group of 24 patients undergoing mUKA surgery following d-MMRT combined with K-L grades 1-3 OA (group 1), and a group of 161 patients who underwent mUKA but presenting with an end-stage bone-on-bone K-L grade 4 OA (group 2). Preoperative and postoperative clinical assessments at one-year follow-up included the Oxford Knee Score (OKS), 5-level EQ-5D version (EQ-5D-5L score), and a standard weight-bearing X-ray protocol. The pairedt-test was used to compare clinical outcomes and radiologic values of the two cohorts and in-between the two cohorts. Statistical significance was set at p < 0.05. The mean follow-up for group 1 was 16.4 ± 2.5 months, and the mean age at the time of operation was 63 ± 8.6 years with a mean time from diagnosis to intervention of 53 ± 47.5 days. Preoperative impairment was greater in group 1 compared to group 2, but with no significant difference. Postoperatively, both groups showed excellent mean outcomes at 1-year follow-up, with no significant difference. The mean preoperative HKA, mPTA, and LDFA were 176.3 ± 3.1, 88.1 ± 2.3, and 86.6 ± 1.7 respectively. The mean postoperative HKA, coronal femoral component angle, and coronal tibial component angle were 179.1 ± 2.6, 87.2 ± 2.3, and 87.2 ± 3.3. No difference was found between preoperative age, BMI, between the two cohorts. Favorable early clinical outcomes were obtained after mUKA in active mid-age and elderly patients presenting with degenerative medial meniscus root tear and mild isolated medial OA. Patients with mild no bone-on-bone OA but with degenerative medial meniscus root tear and medial meniscal extrusion presented the same or worse pre-operative symptoms as patients with end-stage medial OA and benefit the same from mUKA.

Comparison of weight-bearing full-length radiography and three-dimensional computed tomography scan-based models to assess knee joint coronal alignment following total knee arthroplasty

BackgroundThe validity of standing long-leg radiography (LLR) – the standard method for evaluating coronal alignment after total knee arthroplasty (TKA) – remains controversial. We evaluated the measurement reliability and validity of LLR following TKA by comparing postoperative radiographs with three-dimensional computed tomography (3DCT) scans of the lower extremities. MethodsWe retrospectively collected the data of 55 knees from 44 patients who underwent postoperative 3DCT and 5-day and 6-month LLR for coronal alignment evaluation following TKA. The coronal femoral component angle (CFA) and coronal tibial component angle (CTA) were measured using 3DCT and LLR images. Correlations between the hip–knee–ankle angle (HKAA), CFA and CTA were analysed using Pearson’s correlation coefficient (PCC); Bland–Altman plots were constructed to assess agreement between 5-day and 6-month radiographic and 3DCT scan measurements. ResultsThe mean difference in HKAA between 3DCT, and 5-day and 6-month LLR was 1.3 ± 1° and 1.1 ± 0.7°, respectively. Differences of >1° in HKAA between 3DCT, and 5-day and 6-month LLR were observed in 31 (56.4%) and 28 (50.9%) knees, respectively; differences of >2° in these parameters were observed in 15 (27.3%) and nine (16.4%) knees, respectively. The 3DCT scan and radiograph measurements of HKAA, CFA and CTA were strongly correlated (PCC, 0.81–0.92; P < 0.001). Bland–Altman plot validity was within acceptable limits. ConclusionLLR shows good reliability and validity for measuring coronal alignment. When comparing 3DCT scans and radiographs, a high number of HKAA values differed by more than 1° and 2°; this indicates that rigorous alignment evaluation requires 3DCT measurements.

Comparison of the radiographic outcomes and total blood loss between pinless navigation and conventional method in minimally invasive total knee arthroplasty

BackgroundComputer-assisted surgical navigation has been used in total knee arthroplasty (TKA) procedures for years trying to the accuracy of prosthesis placement. We conducted this prospective randomized clinical trial to compare the accuracy of the radiographic parameters of the prosthesis, total blood loss (TBL), and related complications, between a new pinless navigation system (Stryker OrthoMap Express Knee Navigation) and conventional method in patients undergoing minimally invasive (MIS) TKA procedures.Patient and methodsA consecutive series of 100 patients underwent unilateral primary TKA were randomly assigned into two groups: navigation group and convention group. The radiographic parameters of the knee implant and the alignment of lower limb were measured at 3 months after surgery. TBL was calculated according to Nadler’s method. The duplex ultrasonography of both lower limbs was performed in all patients to detect the presence of deep-vein thrombosis (DVT).ResultsTotally, 94 patients have completed the radiographic measures. Only the coronal femoral component angle in the navigation group (89.12° ± 1.83°) had significant differences from that in the convention group (90.09° ± 2.18°) (p = 0.022). There were no differences in the rate of outliers. The mean TBL in the navigation group was 841 ± 267 mL, which was similar to that in the convention group at 860 ± 266 mL (p = 0.721). Postoperative DVT risk did not differ between the two groups (2% vs. 0%, p = 0.315).ConclusionThis pinless navigation TKA showed a comparable acceptable alignment compared with conventional MIS-TKA. There were no differences regarding postoperative TBL between the two groups.

Spacer Block Technique Was Superior to Intramedullary Guide Technique in Coronal Alignment of Femoral Component after Fixed-Bearing Medial Unicompartmental Knee Arthroplasty: A Case-Control Study.

Backgrounds and Objectives: The spacer block technique in unicompartmental knee arthroplasty (UKA) has still a concern related to the precise position of the component in the coronal and sagittal planes compared to intramedullary guide technique. The purposes of this study were to explore whether the spacer block technique would improve the radiological alignment of implants and clinical outcomes compared with the outcomes of the intramedullary guide technique in fixed-bearing medial UKA. Materials and Methods: In total, 115 patients who underwent unilateral, fixed-bearing medial UKA were retrospectively reviewed and divided into group IM (intramedullary guides; n = 39) and group SB (spacer blocks; n = 76). Clinical assessment included range-of-motion and patient-reported outcomes. Radiological assessment included the mechanical femorotibial angle, coronal and sagittal alignments of the femoral and tibial components, and coronal femorotibial congruence angle. Results: All clinical outcomes showed no significant differences between groups. The coronal femoral component angle was valgus 2.4° ± 4.9° in IM group and varus 1.1° ± 3.2° (p < 0.001). In group IM, the number of outlier in coronal femoral component angle (<−10° or 10°<) was 3 cases, while in group SB, there was no outlier (p = 0.014). The coronal femorotibial congruence angle was significantly less in group SB (mean 1.9°, range, −3.2°~8.2°) than in group IM (mean 3.4°, range, −9.6°~16.5°) (p = 0.028). Conclusions: In the group SB, the coronal alignment of femoral component was closer to neutral, and outlier was less frequent than in the group IM. The spacer block technique was more beneficial in achieving proper coronal alignment of the femoral component and congruence of femorotibial components compared to the intramedullary guide technique in fixed-bearing medial UKAs.

Mid-Term Outcomes of Navigation-Assisted Primary Total Knee Arthroplasty Using Adjusted Mechanical Alignment.

The adjusted mechanical alignment (aMA) technique is an extension of conventional mechanical alignment (MA), which has rarely been reported. The purpose of this study was to evaluate mid-term outcomes of navigation-assisted total knee arthroplasty (TKA) using aMA. This retrospective cohort study enrolled 63 consecutive patients (77 knees) who underwent navigation-assisted TKA using aMA between September 2017 and October 2019. Fifty-two consecutive patients (61 knees) who underwent TKA using MA during the same period were assessed as the controlled group. The demographic data and perioperative data were recorded. The parameters of resection and soft tissue balance including tibia resection angle, frontal femoral angle, axial femoral angle, joint line translation, medial and lateral gap in extension and flexion position were recorded. Radiographic parameters and functional scores including the Hospital for Special Surgery (HSS) score, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, and Forgotten Joint Score-12 (FJS-12) were evaluated. Surgery-related complications were recorded. The average follow-up was 3.5 years, with a minimum of 2.4 years. The frontal femoral angle was 2.55° ± 1.08° in aMA group versus 0.26° ± 0.60° in MA group (p < 0.001). The axial femoral angle was 3.07° ± 2.23° external in aMA group versus 2.30° ± 1.70° in MA group (p=0.027). The lateral flexion gap was wider in the aMA group, with a mean of 0.71 mm more laxity (p=0.001). Postoperative coronal alignment was 177.03° ± 1.82° in aMA group versus 178.14° ± 1.69° in MA group (p < 0.001). The coronal femoral component angle was 92.62° ± 2.78° in aMA group versus 90.85° ± 2.01° in MA group (p < 0.001). Both aMA-TKA and MA-TKA achieved satisfactory mid-term clinical outcomes. However, the HSS scores at 1 month postoperatively were significantly higher using aMA than using MA (p < 0.001). Navigation-assisted TKA using aMA technique obtained satisfactory mid-term clinical outcomes. The aMA technique aims to produce a biomimetic wider lateral flexion-extension gap and minimize releases of soft tissues, which might be associated with better early clinical outcomes than MA technique.

Total Knee Arthroplasty Using Adjusted Restricted Kinematic Alignment for the Treatment of Severe Varus Deformity: Technical Note.

ObjectiveTo describe a new alignment technique of adjusted restricted kinematic alignment (arKA) for the treatment of severe varus deformity in total knee arthroplasty.MethodsThree female patients (three severe varus knees) who underwent navigation‐assisted total knee arthroplasty (TKA) using arKA from April 2020 to September 2020 were included in this study, with an average age of 71.33 years (range, 61 to 80 years). General anesthesia was given to all patients. Intraoperative observations including tibia resection angle, frontal femoral angle, axial femoral angle, medial and lateral gap in the extension and flexion positions and joint line translation were recorded. Also, operation duration and drainage volume were recorded. Radiographic parameters including the mechanical axis (α), coronal femoral component angle (β), coronal tibial component angle (γ), sagittal femoral component angle (δ), tibial posterior slope angle (ε), femoral‐patella angle (θ), and femoral notching were assessed. Clinical evaluation was performed using the Hospital for Special Surgery (HSS) Score and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Score. Both individual and mean measurement data were displayed.ResultsThe mean tibial resection was 4.00° varus (range, 3° to 5°), and the mean frontal femoral angle was 3.67° varus (range, 3° to 4°) in extension. The flexion lateral gap was wider than the medial gap with a mean laxity of 1.34 mm. Moreover, the mean axial femoral angle was 2.67° external (range, 0° to 6°) in flexion, and the mean joint line translation was 1.00 mm proximal (range, 0 to 3 mm). In addition, the mean preoperative mechanical axis was 156.22° (range, 153.65° to 158.90°) and the mean postoperative mechanical axis was 174.04° (range, 173.83° to 174.17°) with a mean correction of 17.82°. The mean femoral angle was 92.60° (range, 91.29° to 93.30°) and the mean tibial angle was 86.95° (range, 86.83° to 87.04°) in coronal plane. The HSS score improved from an average of 46.67 points (range, 42 to 51) preoperatively to 83.67 points (range, 81 to 86) at 3 months postoperatively. The mean WOMAC score was 16.33 points at 3 months postoperatively.ConclusionsThe new alignment technique of arKA aims to balance the flexion and extension gap without extensive releases of soft tissue and restore the native pre‐arthritic alignment, may be a promising alignment strategy for treating severe varus deformity. However, further study and comparison with other alignment techniques is needed.

Comparison of alignment and position of prosthesis between portable accelerometer-based navigation device and conventional instrumentation in total knee arthroplasty with valgus deformity

Objective: To explore the differences of alignment and position of prosthesis between portable accelerometer-based navigation device (PAD) and conventional instrumentation (CI) in total knee arthroplasty (TKA) with valgus deformity. Methods: Patients with knee osteoarthritis and valgus deformity who underwent primary TKA in Peking University Third Hospital from January 2017 to December 2020 were enrolled in this retrospective study and were divided into PAD group and CI group according to the surgical instruments. Five male patients and 44 female patients were included with a mean age of (67.2±7.0) years. The differences in preoperative general data, preoperative and postoperative alignment between the two groups were studied. Results: A total of 49 patients (25 patients in the PAD group and 24 in the CI group) were enrolled in this study. There were no statistically significant differences in gender, age, height, weight, body mass index, surgical side, preoperative hip-knee-ankle (HKA) angle, preoperative HKA angle deviation, Keblish classification and Ranawat classification between the two groups (all P>0.05). There was no significant difference in the accuracy of postoperative HKA angle (2.0°±1.4° vs 3.0°±2.2°, P=0.082), coronal femoral component angle (CFCA) (1.5°±1.2° vs 2.1°±1.6°, P=0.144) and coronal tibial component angle (CTCA) (1.2°±0.8° vs 1.3°±1.0°, P=0.695) between the two groups; but the standard deviation of the above-mentioned three indices in PAD group were all smaller than those in CI group. The rate of outliers of postoperative HKA angle of the PAD group was smaller than that in the CI group (P<0.05), but there was no significant difference in the rate of outliers of CFCA and CTCA between the two groups (both P>0.05). Conclusion: TKA assisted by PAD can provide good alignment and prosthesis position in patients with valgus deformity, and it is superior to TKA with CI in terms of precision and rate of outliers of postoperative overall alignment of lower extremity.

Accuracy of different navigation systems for femoral and tibial implantation in total knee arthroplasty: a randomised comparative study.

It remains to be established whether optical computed tomography (CT)-free and acceleration-based navigation systems differ in terms of implantation accuracy and clinical outcomes for total knee arthroplasty. This randomised prospective study compared the implantation accuracy of these two navigation systems in total knee arthroplasty. Optical CT-free navigation (ExactechGPS) or acceleration-based navigation (KneeAlign2) was randomly assigned to the left or right knee of 45 patients who underwent a single-stage bilateral total knee arthroplasty: the ExactechGPS (n = 45) and KneeAlign2 groups (n = 45) were compared. Component alignments were evaluated using three-dimensional computed tomography and radiography at pre- and post-surgery. Implantation accuracy of the component alignment, proportion of outliers, postoperative range of motion, and Japanese Orthopaedic Association (JOA) score were compared between the systems. The implantation accuracies of the lower-extremity mechanical alignment, coronal femoral component angle, coronal tibial component angle, sagittal femoral component, axial femoral angle, and axial tibial angle had no significant difference between the groups. The implantation accuracy of the sagittal tibial component angle was superior in the ExactechGPS than the KneeAlign2 group (1.3° vs. 1.8°, P = 0.034). The proportions of outliers, range of motion, and JOA score had no significant difference between the groups. In the tibial sagittal plane, there was a significant difference in the implantation accuracy, but its difference did not affect the clinical outcomes. Both navigation systems have clinically acceptable implantation accuracy.

Postoperative Functional and Radiological Outcome Comparison of Computer-assisted and Conventional Total Knee Arthroplasty at 6 Months Follow-up: A Cross Sectional Study

Background. Computer-assisted navigation TKA has just been adapted in Indonesia for the last decade. The method is aiming to achieve more precise mechanical alignment in TKA. However, controversies still exist especially in terms of functional outcome and radiological outcome.Method. Fifty elderly patients aged more than 50 years old with severe knee osteoarthritis (Kellgren Lawrence stage III or IV) who scheduled for TKA surgery in the first half of 2019 were consecutively sampled. All patients were measured for objective functional status with Western Ontario Mac Master University Index (WOMAC) and Oxford Knee Score (OKS). Weight-bearing, long-leg follow-up radiographs of both lower limbs were taken, and coronal tibiofemoral angle (CTFA), coronal femoral component angle (CFCA) and coronal tibial component angle (CTCA) were measured.Results. Group of computer-assisted navigation TKA surgery was found to have significantly lower WOMAC score (p0.05) and higher OKS score (p0.05). Although not statistically significant, greater angle of deviation is observed in the conventional TKA surgery group. Proportions with deviation of less than 3º were found more in the group using computer navigation.Discussion. The results of this study indicate the advantage of using a computer assisted system in TKA procedure, in terms of better functional outcome. However, our study only measures mechanical alignment from coronal plane and short term follow up time. Other parameter measurement, such as mechanical alignment on sagittal plane, rotational alignment, and soft tissue balance are also important to determine the success rate of TKA procedure.Conclusion. Patients who had TKA surgery under computer-assisted navigation would benefit a better functional outcome if compared with conventional TKA surgery, as measured with WOMAC and OKS. However, there is no significant difference in terms of radiographic value of coronal-plane mechanical deviation on both methods.

Coronal Alignment of Fixed-Bearing Unicompartmental Knee Arthroplasty Femoral Component May Affect Long-Term Clinical Outcomes

BackgroundThis study aims to investigate the clinical effects of femoral component coronal alignment in a cohort of fixed-bearing unicompartmental knee arthroplasty with clinical and radiological follow-up of 10 years. MethodsProspectively collected registry data of 264 consecutive, cemented, primary fixed-bearing medial unicompartmental knee arthroplasties performed at a single institution from 2004 to 2007 were reviewed. Femoral component coronal angle (FCCA), tibial component coronal angle, and hip-knee-ankle angle were measured on postoperative radiographs. Patients were grouped into acceptable (AG ≤ 3°) and outlier (OG > 3°) groups according to absolute FCCA. Clinical assessment at 6-month, 2-year, and 10-year follow-up was performed using Knee Society Knee and Function Scores, Oxford Knee Score (OKS), and Short Form-36. Fulfillment of expectations, satisfaction, and implant survivorship was recorded. ResultsThere was no significant difference in demographics, tibial component coronal angle, hip-knee-ankle angle, and sagittal parameters in both groups. The OG had poorer OKS at 10 years and a larger deterioration from 2 to 10 years compared to AG (P = .02). Increase in FCCA was associated with deterioration in 2-year OKS (adjusted ß = 0.23, P = .01), 10-year OKS (adjusted ß = 0.26, P = .03), and 2-year Short Form-36 physical component score (adjusted ß = −0.44, P = .01). Expectation fulfillment at 2 years was lower in the OG vs the AG (88% vs 100%, P = .03). Both groups had similar 10-year survivorship (99% vs 98%, P = .65). ConclusionsFCCA may affect long-term clinical outcomes, but not short-term clinical outcomes nor 10-year survivorship. Given similar limb alignment, coronal and sagittal component positioning, a larger FCCA was associated with poorer outcomes at 10-year follow-up.

Similar postoperative outcomes after total knee arthroplasty with measured resection and gap balancing techniques using a contemporary knee system: a randomized controlled trial.

The Attune® Knee System provides new instrumentation to achieve symmetric flexion/extension gaps in total knee arthroplasty (TKA). However, there is limited information on the optimal TKA technique using this system. The aim of this randomised controlled trial was to determine which surgical technique results in better postoperative clinical outcomes after TKA using the contemporary Attune® Knee System: the measured resection or gap balancing technique. A prospective randomized controlled trial was conducted with 100 patients undergoing TKA using measured resection (n = 50) or gap balancing (n = 50) technique. The measured femoral sizer was used in the measured resection group, while the balanced femoral sizer was used in the gap balancing group. Functional outcomes and quality of life were assessed preoperatively and at 6 months and 2 years post-surgery, using the Knee Society Function Score (KSFS), Knee Society Knee Score (KSKS), Oxford Knee Score (OKS), the Physical Component Score (PCS) and Mental Component Score (MCS) of Short-Form 36 (SF-36). Using weight-bearing coronal radiographs, the hip-knee-ankle angle (HKA), coronal femoral component angle (CFA), coronal tibial component angle (CTA) and joint line height were also evaluated for each patient. There were no significant differences in the functional scores or the proportion of patients from each group who were satisfied or had their expectations fulfilled at 6 months or 2 years post-surgery. There was also no significant difference in the number of patients who attained minimum clinically important difference (MCID) postoperatively between the groups. Postoperatively, there was no significant difference in the number of HKA outliers between the groups (p = 0.202). The postoperative CFA (p = 0.265) and CTA (p = 0.479) were similar between the groups. There was also no significant difference in the absolute change (p = 0.447) or proportion of outliers (p = 0.611) for joint line height between the groups. Both measured resection and gap balancing techniques resulted in comparable functional and quality of life outcomes up to 2 years post-surgery. Both techniques appear to be equally effective in achieving excellent outcomes with the Attune® Knee System. I.

Slight under-correction using individualized intentional varus femoral cutting leads to favorable outcomes in patients with lateral femoral bowing and varus knee.

Restoration of neutral alignment is considered key in total knee arthroplasty (TKA). However, this may be undesirable and can result in medial soft-tissue over-release in patients with varus knee and lateral femoral bowing. This study aimed to determine whether individualized intentional varus distal femoral cutting yielded satisfactory clinical and radiological outcomes. A total of 77 patients (91 knees) with varus knee (hip-knee-ankle axis ≥ 10°) and lateral femoral bowing > 5° underwent navigation-assisted primary TKA using individualized intentional varus distal femoral cutting. Knee Society scores, Western Ontario and McMaster Universities scores, and radiographs for limb alignment, implant alignment, and aseptic loosening were evaluated. Subgroup analyses were performed according to the limb alignment and coronal femoral component alignment (0° ± 3° vs. varus of > 3°). All clinical outcomes significantly improved at the final follow-up (p < 0.05 in all). The mechanical axis angle changed from 13.1° ± 2.7° to 2.8° ± 1.5°. The coronal femoral component angle at the final follow-up was 2.8° ± 1.3°. Radiolucent lines were observed in 6 cases (6.6%) and were less than 2mm in all cases without progression. In subgroup analyses, no significant differences were observed in clinical outcomes (n.s. in all) and in the incidence of radiolucent lines (n.s. in limb alignment, n.s. in coronal femoral component alignment). Individualized intentional varus distal femoral cutting yielded favorable clinical outcomes without complications at 5-year follow-up. Slight under-correction using intentional varus distal femoral cutting could be a viable option in patients with varus knee and lateral femoral bowing during navigation-assisted TKA. IV.

Pas de supériorité d’un système de navigation portable par accéléromètre par rapport à une technique conventionnelle en arthroplastie totale du genou: revue systématique et méta-analyse de la littérature

BackgroundPrecise implant alignment is a crucial prognostic factor in total knee arthroplasty (TKA). Portable navigation systems (PN-TKA) were reported to be better than the conventional technique (CON-TKA). We hypothesized that PN-TKA offered greater radiologic precision than CON-TKA in mechanically aligning components. We investigated whether (1) it improved global mechanical alignment, and (2) optimized component placement with respect to the tibial and femoral mechanical axes. Patients and methodsA systematic literature review compared PN-TKA versus CON-TKA. PubMed, Web of Science and Cochrane Library search retrieved ten studies. Their data were pooled using RevMan 5.3. Odds ratios (OR) for dichotomous data were calculated with 95% confidence intervals (CIs) for each outcome. Statistical heterogeneity was assessed as I2 using a standard χ2 test. I2>50% denoted significant heterogeneity requiring a random effects model; otherwise, a fixed effects model was applied. ResultsThere were significantly fewer outliers for mechanical axis (I2=24%, OR=0.62, 95% CI=0.42–0.91, p=0.02) and coronal femoral component angle (I2=58%, OR=0.31, 95% CI=0.13–0.73, p=0.007) using PN-TKA; however, no significant difference was observed for coronal tibial component angle outliers (I2=0%, OR=0.66, 95% CI=0.38–1.15, p=0.14). DiscussionAlthough PN-TKA appeared to improve global alignment, it had no effect on coronal tibial alignment, which is a key factor in predicting the long-term success of component fixation. There thus appeared to be no definite advantage of PN-TKA over CON-TKA. Level of evidenceIII.

No definite advantage of a portable accelerometer-based navigation system over conventional technique in total knee arthroplasty: A systematic review and meta-analysis

BackgroundPrecise implant alignment is a crucial prognostic factor in total knee arthroplasty (TKA). Portable navigation systems (PN-TKA) were reported to be better than the conventional technique (CON-TKA). We hypothesized that PN-TKA offered greater radiologic precision than CON-TKA in mechanically aligning components. We investigated whether (1) it improved global mechanical alignment, and (2) optimized component placement with respect to the tibial and femoral mechanical axes. Patients and methodsA systematic literature review compared PN-TKA versus CON-TKA. PubMed, Web of Science and Cochrane Library search retrieved ten studies. Their data were pooled using RevMan 5.3. Odds ratios (OR) for dichotomous data were calculated with 95% confidence intervals (CIs) for each outcome. Statistical heterogeneity was assessed as I2 using a standard χ2 test. I2>50% denoted significant heterogeneity requiring a random effects model; otherwise, a fixed effects model was applied. ResultsThere were significantly fewer outliers for mechanical axis (I2=24%, OR=0.62, 95% CI=0.42–0.91, p=0.02) and coronal femoral component angle (I2=58%, OR=0.31, 95% CI=0.13–0.73, p=0.007) using PN-TKA; however, no significant difference was observed for coronal tibial component angle outliers (I2=0%, OR=0.66, 95% CI=0.38–1.15, p=0.14). DiscussionAlthough PN-TKA appeared to improve global alignment, it had no effect on coronal tibial alignment, which is a key factor in predicting the long-term success of component fixation. There thus appeared to be no definite advantage of PN-TKA over CON-TKA. Level of evidenceIII.

Effect of Obesity on Component Alignment in Total Knee Arthroplasty.

Obesity is routinely cited as a negative predictive factor for outcomes after total knee arthroplasty (TKA), but the direct mechanism responsible for this relationship has not been described. One possible explanation is a propensity for component malalignment in obese patients that is attributable to difficulty with surgical exposure. This study evaluated the effect of obesity on TKA component alignment in 251 primary TKAs during a 12-month period at a single center in 2009. Postoperative component alignment was retrospectively measured and compared between patients defined as obese (body mass index [BMI] ≥30 kg/m2) and patients defined as nonobese (BMI <30 kg/m2). Alignment was determined by measuring the coronal tibiofemoral angle, coronal femoral component angle, coronal tibial component angle, sagittal femoral component angle, and sagittal tibial component angle in all of the study patients. Statistical analysis failed to demonstrate a statistically significant relationship between obesity and component alignment in any of the measured parameters. The results of this study support that obesity does not negatively affect TKA component alignment; another factor must be associated with the worse outcomes in obese patients undergoing TKA.

Clinical Outcome of Total Knee Arthroplasty Performed Using Patient-Specific Cutting Guides.

BackgroundPatient-specific instruments have recently gained attention for ensuring the accuracy of osteotomy and correct alignment in total knee arthroplasty (TKA). We aimed to report our experience with TKA performed by using CT-based 3D model of cutting guides in our clinic.Material/MethodsA total of 36 patients (mean age, 67.58±8.46 years; 24 females, 12 males) who underwent TKA with 3D patient-specific cutting guides in our clinic were included in the study. Differences between preoperatively planned bone resections and actual bone resections were calculated. Femoral and tibial component angles were measured on radiographs of the knee. The change in knee pain was evaluated by patients on a 10-point visual analog scale (VAS). Patients were followed up for 6 months postoperatively.ResultsThe actual bone resection was 0.5–1.5 mm higher than the planned resection for all sides, being statistically significant for posterior lateral and distal medial sides (1.1±1.3 mm and 1.5±0.9 mm, respectively; p<0.05). On postoperative radiographs, coronal tibial component angle was 88.8°±0.9° and coronal femoral component angle was 95.2°±1.6°, showing good postoperative alignment. The VAS pain score of patients significantly decreased from preoperative 3.9±0.8 to 1.1±0.9 at 6 months after the operation. One patient developed superficial tissue infection on postoperative follow-up, which was effectively treated. No other pathology was detected in the postoperative period.ConclusionsPatient-specific cutting guides can provide intraoperative guidance for better placement of the implant in TKA and increase the accuracy of osteotomy and postoperative alignment.

Incurvation frontale des os longs du membre inférieur : son influence sur l’axe frontal et le positionnement des implants dans les arthroplasties du genou sans navigation et ancillaire conventionnel

BackgroundCoronal alignment is an important factor for the function and longevity of total knee arthroplasty (TKA). Coronal bowing of the lower extremity is common among Asians and it may pose a risk for malalignment of the lower leg and malposition of component. HypothesisWe hypothesized that coronal bowing itself has a risk for malalignment of the lower leg and malposition of femoral/tibial components and that navigation TKA is beneficial for patients with coronal bowing. We investigated the incidence of femoral/tibial bowing in patients treated with TKA and compared the radiographic parameters between the navigation group and the conventional group. Additionally, the influence of coronal bowing on these radiographic parameters was investigated. Materials and methodsWe enrolled 35 patients with knee osteoarthritis and 70 bilateral simultaneous TKAs. The patients underwent TKA with the use of a computer tomography-free navigation in one knee and conventional TKA in the contralateral knee. Preoperative coronal bowing were measured, and the subjects were divided into 2 subgroups, i.e. the bowing group and the non-bowing group. Lateral bowing was expressed as plus (+) and medial bowing was expressed as minus (–). Various radiographic parameters, including coronal bowing, lower leg alignment, component position, and outliers were compared between the navigation group and the conventional group. ResultsFemoral bowing varied from –7.4° to 10.9° with an average of 3.0°. Tibial bowing varied from –4.1° to 4.6° with an average of 0.4°. The femoral component was placed more properly in the navigation group. Number of outlier regarding to the coronal femoral component angle to the femoral mechanical axis was 14 cases (37.8 %) in the bowing group and 6 cases (18.2 %) in the non-bowing group (P=0.04). DiscussionIn conclusion, coronal femoral bowing has an important effect on femoral bone cut in TKA. The navigated TKA was more consistent than conventional TKA in aiding proper alignments of femoral component. Level of evidenceLevel II, comparative prospective study.

The accuracy of a hand-held navigation system in total knee arthroplasty.

This study aims to evaluate the effectiveness of a new hand-held navigation system. The authors of this study hypothesize that this navigation system will improve overall lower limb alignment and implant placement without causing a delay in surgery. Two hundred consecutive patients diagnosed with tricompartmental osteoarthritis and underwent total knee arthroplasty by a senior surgeon were included in this study. One hundred patients underwent TKA using the hand-held navigation system, while the other 100 patients underwent TKA using the conventional technique. The primary outcomes of this study were the overall alignment of the lower limb and the position of the components. This was determined radiologically using the: (1) Hip-Knee-Ankle angle (HKA) for lower limb alignment; (2) Coronal Femoral-Component angle (CFA); and (3) Coronal Tibia-Component angle (CTA) for component position. Normal alignment was taken as 180°±3° for the HKA and 90°±3° for both the CFA and CTA. For the CFA, the proportion of outliers was 7 and 17% in the hand-held navigation and conventional group, respectively (p=0.030). For the HKA and CTA, there was no difference in the proportion of outliers between the two groups. The duration of surgery was 73±9min and 87±15min in the hand-held navigation and conventional group, respectively (p<0.001). This hand-held navigation system is an effective intraoperative tool for reducing the proportion of outliers for femoral implant placement as well as the duration of surgery. The authors conclude that it can be considered for use to check femoral implant placement intra-operatively. III.

Influence of coronal bowing on the lower alignment and the positioning of component in navigation and conventional total knee arthroplasty

BackgroundCoronal alignment is an important factor for the function and longevity of total knee arthroplasty (TKA). Coronal bowing of the lower extremity is common among Asians and it may pose a risk for malalignment of the lower leg and malposition of component. HypothesisWe hypothesized that coronal bowing itself has a risk for malalignment of the lower leg and malposition of femoral/tibial components and that navigation TKA is beneficial for patients with coronal bowing. We investigated the incidence of femoral/tibial bowing in patients treated with TKA and compared the radiographic parameters between the navigation group and the conventional group. Additionally, the influence of coronal bowing on these radiographic parameters was investigated. Materials and methodsWe enrolled 35 patients with knee osteoarthritis and 70 bilateral simultaneous TKAs. The patients underwent TKA with the use of a computer tomography-free navigation in one knee and conventional TKA in the contralateral knee. Preoperative coronal bowing were measured, and the subjects were divided into 2 subgroups, i.e. the bowing group and the non-bowing group. Lateral bowing was expressed as plus (+) and medial bowing was expressed as minus (−). Various radiographic parameters, including coronal bowing, lower leg alignment, component position, and outliers were compared between the navigation group and the conventional group. ResultsFemoral bowing varied from −7.4° to 10.9° with an average of 3.0°. Tibial bowing varied from −4.1° to 4.6° with an average of 0.4°. The femoral component was placed more properly in the navigation group. Number of outlier regarding to the coronal femoral component angle to the femoral mechanical axis was 14 cases (37.8%) in the bowing group and 6 cases (18.2%) in the non-bowing group (P=0.04). DiscussionIn conclusion, coronal femoral bowing has an important effect on femoral bone cut in TKA. The navigated TKA was more consistent than conventional TKA in aiding proper alignments of femoral component. Level of evidenceLevel II, comparative prospective study.

Computer-assisted stereotaxic navigation improves the accuracy of mechanical alignment and component positioning in total knee arthroplasty.

This study reports on a novel computer-assisted stereotaxic navigation (CASN) system that attempts to combine the accuracy of computer navigation with familiarity of conventional methods. We hypothesize that CASN would improve mechanical alignment and component positioning when compared to conventional instrumentation. 145 patients (192 knees) retrospectively matched for age, BMI, gender and pre-operative scores, underwent total knee arthroplasty (TKA) using CASN (n=92) or conventional instrumentation (n=100). Pre- and post-operative radiological alignment [Acceptable ranges: mechanical axis (MA) 0°±3°, coronal femoral-component angle (CFA) and coronal tibia-component angle (CTA) 90°±3°] and clinical outcomes (Knee Society Scores, Oxford Knee Score and Short Form-36) at 6months were examined. The CASN group had significantly improved mean MA (1.9°±1.4°, versus 2.8°±2.0° in the conventional group, p=0.001), CFA (1.6°±1.3°, versus 2.1°±1.5° in the conventional group, p=0.035) and CTA (1.6°±1.2°, versus 2.1°±1.5° in the conventional group, p=0.024). 91.3% of knees in the CASN group were within 3° of a neutral mechanical axis, versus 74% in the conventional group (p<0.001). The duration of surgery was significantly longer in the CASN group (84±22 vs 73±15min, p=0.001) and cost an additional USD 850 per operation. There were no significant differences in clinical outcomes or satisfaction rates at 6months post-operatively (p>0.05). CASN improved TKA mechanical alignment and component positioning, however, resulted in longer and costlier surgery with no benefits in short-term functional outcomes, despite providing familiarity to surgeons accustomed to conventional instrumentation. III.