The accuracy of extramedullary guides for tibial component placement in total knee arthroplasty

Pressure change at ankle joint in supramalleolar osteotomy with or without fibular osteotomy according to different types of varus ankle

The need for additional fibular osteotomy (FO) when performing supramalleolar osteotomy (SMO) in the varus ankle arthritis (VAA) is controversial. Some cadaveric studies have been performed to prove this; however, it is difficult to implement deformities including talar tilting and translation in cadavers. In this study, we created a model of VAA with the tilting and translation using three-dimensional (3-D) finite element (FE) analysis and analyzed the results of SMO with or without FO depending on the types of VAA. The validated normal foot and ankle 3-D FE model was constructed including the ankle cartilages of the talar dome and tibia plafond. The VAA models were determined and reconstructed by following the classification of VAA, VAA with medial translation for stage 3a, VAA with varus tilting (7.5°) for stage 3b. The postoperative SMO models (SMO with and without FO) were reconstructed by corresponding to each VAA models. The FE analysis conditions were commonly applied. The boundary condition of ankle joint was defined as "sliding condition" and applied 0.002 friction coefficient to realize lubricative property. Loading condition was assumed as a two-leg standing position and half of the subject body weight (325 N) was loaded on center of ground to vertical direction. Contact pressure changes were predicted at the medial ankle cartilage. As a result, in VAA with medial translation, isolated SMO may provide sufficient pressure reduction at the medial ankle joint. However, in VAA with varus tilting, SMO combined with FO could appropriately relieve concentrated pressure at the medial ankle joint.

Prevalence of extra-articular tibia valga morphology in valgus knees and its implications for primary total knee arthroplasty

INTRODUCTION

Tibia valga, an extra-articular valgus deformity of the tibia, is common in valgus knees and can result in component misplacement and early total knee arthroplasty (TKA) failure. However, the prevalence and importance of tibia valga in TKA have been seldom reported. This study aims to describe the prevalence and characteristics of tibia valga morphology in valgus knees and describe implications for surgical planning in primary TKA.

METHODS

We prospectively examined pre-operative weightbearing whole-body EOS digital radiographs of patients with knee osteoarthritis listed for TKA between December 2018 and December 2020. Hip-knee-ankle angle (HKA), mechanical lateral distal femoral angle (mLDFA), mechanical medial proximal tibial angle (mMPTA), joint line convergence angle (JLCA) and tibial morphology with centre of rotation of angulation of tibia (CORA-tibia) were measured and analysed.

RESULTS

In 830 knees, 253 (30%) and 577 (70%) were classified as valgus and varus, respectively. In valgus knees, 89 knees (35%) had tibia valga. Median CORA-tibia was 2.8° (range 0.2°-10.9°). Tibia valga knees had no difference in mLDFA, higher HKA (5.0^o versus 3.0°, p = 0.002) and mMPTA (89.6° versus 88.1°, p < 0.01), and lower JLCA (2.1° versus 2.3°, p < 0.01) compared to non-tibia valga knees. Tibia valga deformity was weakly positively correlated with valgus HKA (ρ = 0.23, p < 0.001) and mMPTA (ρ = 0.38, p < 0.001). In varus knees, there were 52 cases of tibia valga (9%) with median CORA-tibia of 3.0° (range 0.5°-5.5°). Tibia valga knees had higher mMPTA (87.0° versus 85.2°, p < 0.05) and no difference in HKA, mLDFA and JLCA. CORA-tibia was weakly positively correlated with mMPTA.

CONCLUSIONS

Valgus knees may have an extra-articular deformity of the tibia which might be the primary contributor of the overall valgus HKA deformity rather than the distal femoral anatomy. To detect the deformity, full leg-length radiographs should be acquired pre-operatively. Intramedullary instrumentation should be used cautiously in knees with tibia valga when performing TKA.

Comparison of tibial alignment parameters based on clinically relevant anatomical landmarks : a deep learning radiological analysis

AIMS

Accurate identification of the ankle joint centre is critical for estimating tibial coronal alignment in total knee arthroplasty (TKA). The purpose of the current study was to leverage artificial intelligence (AI) to determine the accuracy and effect of using different radiological anatomical landmarks to quantify mechanical alignment in relation to a traditionally defined radiological ankle centre.

METHODS

Patients with full-limb radiographs from the Osteoarthritis Initiative were included. A sub-cohort of 250 radiographs were annotated for landmarks relevant to knee alignment and used to train a deep learning (U-Net) workflow for angle calculation on the entire database. The radiological ankle centre was defined as the midpoint of the superior talus edge/tibial plafond. Knee alignment (hip-knee-ankle angle) was compared against 1) midpoint of the most prominent malleoli points, 2) midpoint of the soft-tissue overlying malleoli, and 3) midpoint of the soft-tissue sulcus above the malleoli.

RESULTS

A total of 932 bilateral full-limb radiographs (1,864 knees) were measured at a rate of 20.63 seconds/image. The knee alignment using the radiological ankle centre was accurate against ground truth radiologist measurements (inter-class correlation coefficient (ICC) = 0.99 (0.98 to 0.99)). Compared to the radiological ankle centre, the mean midpoint of the malleoli was 2.3 mm (SD 1.3) lateral and 5.2 mm (SD 2.4) distal, shifting alignment by 0.34^o (SD 2.4^o) valgus, whereas the midpoint of the soft-tissue sulcus was 4.69 mm (SD 3.55) lateral and 32.4 mm (SD 12.4) proximal, shifting alignment by 0.65^o (SD 0.55^o) valgus. On the intermalleolar line, measuring a point at 46% (SD 2%) of the intermalleolar width from the medial malleoli (2.38 mm medial adjustment from midpoint) resulted in knee alignment identical to using the radiological ankle centre.

CONCLUSION

The current study leveraged AI to create a consistent and objective model that can estimate patient-specific adjustments necessary for optimal landmark usage in extramedullary and computer-guided navigation for tibial coronal alignment to match radiological planning.Cite this article: Bone Jt Open 2022;3(10):767-776.

Rethinking the Coronal Anatomic Axis of the Distal Tibia for Intramedullary Nail Placement: A Cadaveric Study

Background: Recent studies have reported that targeting a center-center position at the distal tibia during intramedullary nailing (IMN) may result in malalignment. Although not fully understood, this observation suggests that the coronal anatomic center of the tibia may not correspond to the center of the distal tibia articular surface. Questions/Purposes: To identify the coronal anatomic axis of the distal tibia that corresponds to an ideal start site for IMN placement utilizing intact cadaveric tibiae. Methods: IMN placement was performed in 9 fresh frozen cadaveric tibiae. A guidewire was used to identify the ideal start site in the proximal tibia and an opening reamer allowed access to the canal. Each nail was then advanced without the use of a reaming rod until exiting the distal tibia plafond. Cadaveric and radiographic measurements were performed to determine the center of the nail exit site in the coronal plane. Results: Cadaveric and radiographic measurements identified the IMN exit site to correspond with the lateral 59.5% and 60.4% of the plafond, respectively. Conclusions: Tibial nails inserted using an ideal start site have an endpoint that corresponds roughly to the junction of the lateral and middle third of the plafond. Further studies are warranted to better understand the impact of IMN endpoint placement on the functional and radiographic outcomes of tibia shaft fractures.

Prevalence of proximal tibia vara in Indonesian population with knee osteoarthritis

BACKGROUND

Proximal tibia vara has drawn interest since the concept of constitutional varus was introduced. Proximal tibia vara is a condition where the knee varus tilt the tibia condyle medially and shift the tibial articular surface medially. This condition affects medial proximal tibial angle measurements and the placement of the tibial implant in knee replacement surgery. Thus, it challenged the neutral knee arthroplasty alignment target because some people may present a proximal tibia vara. This study assesses the prevalence of the proximal tibia vara and the correlation to knee osteoarthritis grade.

METHODS

This retrospective study was carried out from January 2021 to June 2021. Eighty-five limbs were included with the following inclusion criteria: knee osteoarthritis patients who received a long view lower extremity radiograph. The exclusions criteria were (1) patients who had undergone arthroplasty and lower extremity surgery before and (2) valgus knee deformity. The outcomes in this study were HKAA, MAD, TAD, MPTA, PTRP, LDFA, and PTS. Intraclass correlation (ICC) using two-way mixed was used to assess the reproducibility of the radiographic parameters. Multiple logistic regression was used to evaluate the correlation between knee osteoarthritis grade and radiographs parameters (MAD and TAD).

RESULT

A total 85 limbs from 52 patients were assessed in this study. Proximal tibia vara was found in 18 knees (21%.). The logistic regression was performed to assess the correlation between the severity of the knee osteoarthritis and radiographic parameters (MAD, TAD, LDFA, and PTS) with an overall p-value < 0.001 and pseudo-R² = 0.29.

CONCLUSION

A significant portion of patients with knee osteoarthritis have proximal tibia vara, and it is a pre-existing condition. Since the pre-existing proximal tibia vara affects preoperative measurements, a long-standing lower extremity x-ray is recommended to be obtained as part of knee replacement preparation.

[Value of personalized extramedullary positioning technique on tibia side for coronal alignment of tibial prosthesis in total knee arthroplasty]

OBJECTIVE

To explore the coronal alignment of tibial prosthesis after osteotomy using personalized extramedullary positioning technique on tibia side in total knee arthroplasty (TKA).

METHODS

A clinical data of 170 patients (210 knees) who underwent primary TKA between January 2020 and June 2021 and met the selection criteria was retrospectively analyzed. Personalized and traditional extramedullary positioning techniques were used in 93 cases (114 knees, personalized positioning group) and 77 cases (96 knees, traditional positioning group), respectively. The personalized extramedullary positioning was based on the anatomical characteristics of the tibia, a personalized positioning point was selected as the proximal extramedullary positioning point on the articular surface of the tibial plateau. There was no significant difference between the two groups in gender, age, body mass index, surgical side, course of osteoarthritis, and Kellgren-Lawrence classification ( P>0.05). The preoperative tibial bowing angle (TBA) formed by the proximal and distal tibial coronal anatomical axes in the personalized positioning group was measured and the tibia axis was classified, and the distribution of personalized positioning point was analyzed. The pre- and post-operative hip-knee-ankle angle (HKA), the lateral distal tibial angle (LDTA), and the postoperative tibia component angle (TCA), the excellent rate of tibial prosthesis alignment in coronal position were compared between the two groups.

RESULTS

In the personalized positioning group, 58 knees (50.88%) were straight tibia, 35 knees (30.70%) were medial bowing tibia, and 21 knees (18.42%) were lateral bowing tibia. The most positioning points located on the highest point of the lateral intercondylar spine (62.07%) in the straight tibia group, while in the medial bowing tibia and lateral bowing tibia groups, most positioning points located in the area between the medial and lateral intercondylar spines (51.43%) and the lateral slope of the lateral intercondylar spine (57.14%), respectively. The difference in HKA between pre- and post-operation in the two groups was significant ( P<0.05); while the difference in LDTA was not significant ( P>0.05). There was no significant difference in preoperative LDTA and HKA and the difference between pre- and post-operation between groups ( P>0.05). But there was significant difference in postoperative TCA between groups ( P<0.05). The postoperative tibial plateau prosthesis in the traditional positioning group was more prone to varus than the personalized positioning group. The excellent rates of tibial prosthesis alignment in coronal position were 96.5% (110/114) and 87.5% (84/96) in personalized positioning group and traditional positioning group, respectively, showing a significant difference between groups ( χ ²=7.652, P=0.006).

CONCLUSION

It is feasible to use personalized extramedullary positioning technique for coronal osteotomy on the tibia side in TKA. Compared with the traditional extramedullary positioning technique, the personalized extramedullary positioning technique has a higher excellent rate of tibial prosthesis alignment in coronal position.

Achieving coronal plane alignment in total knee arthroplasty through modified preoperative planning based on long-leg radiographs: a prospective study

Purpose

This prospective study was undertaken to examine whether the desired coronal plane alignment of limb and prosthetic components in total knee arthroplasty (TKA) could be achieved precisely using conventional jig-based methods by modifying the preoperative planning of bone resection utilizing long-leg radiographs (LLRs).

Methods

The study included consecutive 245 TKA procedures. Pre- and postoperative radiological variables, i.e., the mechanical axis (hip-knee-ankle [HKA] axis), mechanical lateral distal femoral angle (mLDFA), and medial proximal tibial angle (MPTA), and their outliers were evaluated. Statistical analysis was performed using SPSS version 21.0.

Results

The mean postoperative HKA axis, mLDFA and MPTA was 179.80 ± 1.81° (p < 0.01; 95% CI: 8.09–9.67), 90.35 ± 1.54° (p < 0.01; 95% CI: 1.33–2.02), and 90.26 ± 1.25° (p < 0.01; 95% CI: 4.41–5.20), respectively. The postoperative HKA axis on the coronal plane was 180 ± 3° in 235 knees (95.92%, 4.08% outliers). Femoral and tibial components were implanted in an acceptable position, withing 90 ± 3° of the mechanical axis of the femur and tibia on the coronal plane in 238 (97.14%, 2.86% outliers) and 243 (99.18%, 0.8% outliers) knees, respectively.

Conclusion

Modified preoperative planning for TKA on LLRs is a reliable and consistent method to achieve the desired limb and component alignment on the coronal plane without adding financial or logistical costs.

Level of evidence

II

Tibia vara in Asians: Myth or fact? Verification with three-dimensional computed tomography

BACKGROUND

There is a common perception among surgeons that Asian tibiae are significantly more varus compared to non-Asians, contributed both by an acute medial tibial proximal angle (MPTA) and diaphyseal bowing. Insight into the normative morphology of the tibia allows generation of knowledge towards disease processes and subsequently planning for corrective surgeries.

METHODS

Computed tomography (CT) scans of 100 normal adult knees, aged 18 years and above, were analysed using a 3-dimensional (3D) analysis software. All tibiae were first aligned to a standard frame of reference and then rotationally aligned to the tibial centroid axis (TCAx) and the transmalleolar axis (tmAx). MPTA was measured from best-fit planes on the surface of the proximal tibia for each rotational alignment. Diaphyseal bowing was assessed by dividing the shaft to three equal portions and establishing the angle between the proximal and distal segments.

RESULTS

The mean MPTA was 87.0° ± 2.2° (mean ± SD) when rotationally aligned to TCAx and 91.6° ± 2.7° when aligned to tmAx. The mean diaphyseal bowing was 0.1° ± 1.9° varus when rotationally aligned to TCAx and 0.3° ± 1.6° valgus when aligned to tmAx. The mean difference when the MPTA was measured with two different rotational alignments (TCAx and tmAx) was 4.6° ± 2.3°. No statistically significant differences were observed between males and females. Post hoc tests revealed statistically significant difference in MPTA between different ethnic sub-groups.

CONCLUSION

The morphology of the proximal tibiae in the disease-free Asian knee is inherently varus but not more so than other reported populations. The varus profile is contributed by the MPTA, with negligible diaphyseal bowing. These implications are relevant to surgical planning and prosthesis design.

Postoperative radiologic outcome comparison between conventional and computer-assisted navigation total knee arthroplasty in extra-articular tibia vara

PURPOSE

Total knee arthroplasty (TKA) is the definite treatment for osteoarthritis. Meanwhile, significant inherent extra-articular varus angulation is associated with abnormal postoperative hip-knee-ankle (HKA) angle. Computer-assisted navigation TKA (CAS-TKA) used in patients who have severe varus deformity. The purpose of this study was to compare postoperative radiologic outcome between CAS-TKA and conventional TKA for extra-articular tibia vara.

METHODS

A retrospective review of postoperative HKA on standing lower extremity views was conducted in patients who underwent TKA by a single surgeon from 2010 to 2018, including knee with conventional TKA (n = 83) and CAS-TKA (n = 246). Extra-articular tibia vara was assessed by measuring the metaphyseal-diaphyseal angle (MDA) of the tibia in preoperative standing lower extremity view. Postoperative alignment was assessed by measuring the HKA in postoperative standing lower extremity view.

RESULTS

There was no significant difference in age (p = 0.063), gender (p = 0.628), body mass index (p = 0.426), preoperative range of motion (p = 0.524), preoperative HKA (p = 0.306), preoperative MDA (p = 0.523), or postoperative HKA (p = 0.416) between the two groups (conventional TKA and CAS-TKA). There was no significant difference in postoperative alignment for cases with MDA ≤4° (p = 0.351) or MDA >4° (p = 0.866) in each group. There was a positive correlation between preoperative HKA and postoperative HKA in the CAS-TKA group (p < 0.001, r = 0.243). However, there was no significant correlation between preoperative HKA and postoperative HKA in the conventional TKA group (p = 0.732).

CONCLUSIONS

There was no significant difference in postoperative alignment between conventional TKA and CAS-TKA in extra-articular tibial vara even for cases with MDA >4°.

Tibial bowing and tibial component placement in primary total knee arthroplasty in valgus knees: Are we overlooking?

PURPOSE

Tibial bowing in valgus knees with arthritis can lead to component malplacement during total knee arthroplasty (TKA). Incidence of valgus knees with medial tibial bowing, its effect on tibial component placement during primary TKA and methods to improve accuracy of the component placement were studied.

METHODS

Full-length weight-bearing alignment radiograph was taken in 117 patients (149 knees) with valgus deformity undergoing TKA. In these cases, the proximal tibial reference for extramedullary jig placement was planned preoperatively with reference to the tibial spines and classified as four zones.

RESULTS

The mean preoperative hip-knee-ankle (HKA) angle was 192.9° (180.3-234.5°). Bowing >3° was considered significant (p < 0.001) and at this level of bowing, the proximal tibial reference was shifted from centre to medial. Tibial bowing <3° was considered straight and >3° as tibia valga. Tibia was bowed in 70 knees (46.97%). Severity of valgus deformity had strong positive correlation with the tibia valga (p < 0.001). The post-operative medial proximal tibial angle (MPTA) and HKA angle were 91.63° (87.9-95.7°) and 182.6° (178.1-189.7°), respectively. The mean MPTA and post-operative HKA angle in bowed and straight tibiae were 90.35° versus 89.78° (p = 0.547) and 181.5° versus 180.7° (p = 0.5716), respectively, and the difference was not statistically significant.

CONCLUSION

Medial tibial bowing is very common in valgus knees. Tibia valga has a strong positive correlation with the severity of valgus deformity. Accurate tibial component placement can be achieved with a medialized reference point for extramedullary tibial cutting jig in knees with significant tibia valga. The study has been registered in clinical trials registry - India (CTRI/2018/03/012283).

Revisiting the tibial crest as reference for the mechanical alignment of the tibial component in total knee arthroplasty: a cadaveric study on Caucasian tibiae

PURPOSE

The accuracy of the tibial crest (TC) in guiding the mechanical alignment of the tibial component in total knee arthroplasty (TKA) has been investigated in a few studies on Asian patients. No study analyzed the anatomical variants of the TC. We analyzed the morphological types of the TC in cadaveric tibiae of Caucasian subjects and assessed whether the TC may be considered an accurate guide for the mechanical alignment of the tibial component in TKA.

METHODS

The TC and mechanical axis (MA) were identified in 86 dried cadaveric tibiae by placing metal landmarks along the TC course and a guidewire overlapping the MA. Coronal view radiographs were taken in different positions of tibial axial rotation, and the relationships between the TC and MA were analyzed.

RESULTS

The TC showed three different patterns, comprising a curved, mixed and straight course in 47 (54.6%), 21 (24.4%) and 18 (20.9%) tibiae, respectively. When a curved course was found, the TC intersected the MA at proximal and distal points located, on average 22.4% and 63.3% along the tibial length, respectively. When a straight course was found, the mean angle between the TC and MA was 2.9°. In 35% of the cases, the two axes differed by more than 3°.

CONCLUSION

The TC of Caucasian subjects exhibits a marked variability in its course and relationship with the MA. Unlike the TC in Asian subjects, the TC of Caucasians cannot be considered an accurate anatomical reference to guide the coronal alignment of the tibial component in TKA.

The native coronal orientation of tibial plateaus may limit the indications to perform a kinematic aligned total knee arthroplasty

PURPOSE

To investigate the coronal alignment of tibial plateaus in normal and osteoarthritic knees and to simulate the effects of a tibial cut performed in total knee arthroplasty (TKA) using a kinematic alignment technique with standard instrumentation.

METHODS

The coronal alignment of tibial plateaus was measured in three groups including group 1 (reference group), 50 cadaveric tibiae showing no evidence of degenerative changes of tibial plateaus; group 2, 49 patients who underwent MR of the knee, showing no or mild degenerative changes of the knee joint and, group 3, 54 patients with knee osteoarthritis who underwent computer-assisted total knee arthroplasty.

RESULTS

The coronal alignment of tibial plateaus averaged 2.4° with no significant differences between groups. The mean coronal orientation of tibial plateaus was 3° ± 2° in men and 1.6° ± 2° in women (p = 0.03). A coronal alignment of tibial plateaus of 3° or more was found in 69 cases (45%) and 5° or more in 23 (14.7%). The simulation of a tibial cut performed with an error of 3° in varus in 15% of the subjects showing a native coronal orientation of tibial plateaus of 3° or more, led to a final tibial cut greater 6° in 13.7% of cases.

CONCLUSIONS

A coronal alignment of tibial plateaus of 3° or more in varus was found in near half of normal subjects and osteoarthritic patients. A preoperative measurement of the coronal alignment of tibial plateaus is advisable in any patients scheduled for kinematic aligned TKA. As errors in the alignment of the tibial component of 3° or more may occur using standard instrumentations, the results of this study raise questions on performing a kinematic aligned TKA with standard instrumentations.

LEVEL OF EVIDENCE

IV.

Total knee replacement modifies the preoperative tibial torsion angle-similar results between computer-assisted and standard technique

Background

Malpositioning of the components in total knee replacement (TKR) can result in failure or deficient outcomes of the surgical procedure. In the tibial segment, the rotational position of the tray should reproduce the mechanical axis without modifying physiological tibial torsion.

Methods

A randomised, prospective study was made of 74 patients subjected TKR involving the standard technique (38 cases) and navigation surgery (36 cases). A computed tomography study of the knee and ankle was made before the operation and after arthroplasty implantation, in order to identify the position of the prosthetic tibial tray in the transverse axis and the tibial torsion angle.

Results

The rotation of the tibial tray changed from its preoperative to postoperative range, but no significant differences were found between the navigated and the standard groups. The presence of preoperative deformities in the frontal plane did not modify the changes in the rotation of the tibial component. The mean preoperative tibial torsion angle was 17.76º (SD =10.15) of external rotation, with no significant differences in relation to the previous frontal deformity. After TKR, the tibial torsion angle was 15.36º (SD =7.16) (P=0.021). There were no differences in final tibial torsion between the knees operated upon with the standard instruments and those subjected to computer-assisted surgery (CAS; P=0.157).

Conclusions

TKR surgery modifies preoperative tibial torsion. Neither mechanical instrumentation nor navigation surgery precisely reproduces the rotational axis of the leg.

Lateralization of Tibial Plateau Reference Point Improves Accuracy of Tibial Resection in Total Knee Arthroplasty in Patients with Proximal Tibia Vara

Background

The tibial cut referenced to the center of the intercondylar eminence often leads to varus malalignment in the presence of preexisting proximal tibia vara. The purpose of this study was to investigate the effect of lateralization of the lateral tibial plateau reference point (based on the amount of proximal tibia vara) on the postoperative coronal plane alignment.

Methods

In this prospective cohort study, 62 patients (95 knees) with osteoarthritis and proximal tibia vara underwent primary total knee arthroplasty using a lateral tibial plateau reference point for the extramedullary jig. The pre- and postoperative radiographs were obtained for measurement of mechanical axis deviation, degree of tibia vara, proximal lateral reference point of the tibial condyle, and coronal alignment of the femoral and tibial components. The distance between the tibial reference point and the center of the intercondylar eminence was measured intraoperatively.

Results

The mean tibia vara was 7.1° (standard deviation [SD], 2.3°). The mean lateral displacement of the reference point was 7 mm (SD, 2.2 mm). Postoperative tibiofemoral angle was 6° to 10° of valgus in 94% of cases. There was a strong correlation between the magnitude of tibia vara and the amount of lateralization of the tibial reference point (R² = 0.79, p < 0.001).

Conclusions

In total knee arthroplasty patients with proximal tibia vara, reasonable accuracy can be achieved with use of the extramedullary jig for tibial component alignment by lateralizing the proximal tibial reference point.

Effect of Femoral Resection on Coronal Overall Alignment after Conventional Total Knee Arthroplasty

Background:

A good postoperative alignment in total knee arthroplasty (TKA) is the key to achieving satisfactory results. We assessed the effect of femoral and tibial resection on the overall alignment after conventional TKA.

Methods:

We conducted a retrospective analysis of 212 primary TKAs in 188 patients. Intramedullary (IM)-guided resection was applied on the femoral side while extramedullary (EM)-guided resection was used on the tibial side. Using full-length X-ray, the preoperative femoral valgus angle and lower extremity alignment, as well as 2-week postoperative femoral and tibial prosthetic coronal alignment and overall lower extremity alignment, were measured.

Results:

Postoperatively, good prosthetic alignment was achieved in 191 cases (90.1%) on the tibial side and in 144 cases (67.9%) on the femoral side (χ² = 5.441, P = 0.02). Multiple linear regression analysis was used to assess the effect of different alignment sides on the overall alignment in the coronal plane. Data were divided into five subgroups based on the valgus or varus status of the prostheses. The standardized regression coefficients of the femoral and tibial prosthetic alignment on the overall alignment were 0.666 and 0.414, respectively; in varus on both sides were 0.658 and 0.377, respectively; in valgus, 0.555 and 0.030; femoral side varus and tibial side valgus, 0.702 and 0.211; femoral side valgus and tibial side varus, −0.416 and 0.287. The study showed that the overall low extremity alignment was statistically influenced by the prosthetic alignment, except for the tibial prosthetic alignment when femoral prosthesis was in valgus (P = 0.153).

Conclusions:

In conventional TKA, tibial side EM-guided resection may offer satisfactory postoperative alignment, and femoral resection relying on IM guide may lead to more undesirable results. Postoperative coronal alignment is mainly affected by the femoral resection. Therefore, femoral side operation should receive adequate attention from the surgeons.

Preoperative Measurement of Tibial Resection in Total Knee Arthroplasty Improves Accuracy of Postoperative Limb Alignment Restoration

Background:

Accuracy of implant placement in total knee arthroplasty (TKA) is crucial. Traditional extramedullary alignment instruments are fairly effective for achieving the desired mean tibial component coronal alignment. We modified the traditional tibial plateau resection technique and evaluated its effect on alignment restoration.

Methods:

Two hundred and eighty-two primary TKAs in our hospital between January 2013 and December 2014 were enrolled in this retrospective study. Group A consisted of 128 primary TKAs performed by one senior surgeon. Preoperative measurement of the tibial resection was conducted on radiographs, and the measured thicknesses of the lateral and medial plateau resection were used to place the tibial alignment guide. Group B consisted of 154 primary TKAs performed by the other senior surgeon, using a traditional tibial plateau resection technique. In all patients, an extramedullary guide was used for tibial resection, and preoperative and postoperative full-leg standing radiographs were used to assess the hip-knee-ankle angle (HKA), femoral component alignment angle (FA), and tibial component alignment angle (TA). A deviation ≥3° was considered unsatisfactory. Data were analyzed by unpaired Student's t-test.

Results:

The mean postoperative HKA and TA angles were significantly different between Groups A and B (178.2 ± 3.2° vs. 177.0 ± 3.0°, t = 2.54, P = 0.01; 89.3 ± 1.8° vs. 88.3 ± 2.0°, t = 3.75, P = 0.00, respectively). The mean postoperative FA was 88.9 ± 2.5° in Group A and 88.9 ± 2.6° in Group B, and no significant difference was detected (t = 0.10, P = 0.92). There were 90 (70.3%) limbs with restoration of the mechanical axis to within 3° of neutral alignment and 38 (29.7%) outliers (>3° deviation) in Group A, whereas there were 89 (57.8%) limbs with restoration of the mechanical axis to within 3° of neutral alignment and 65 (42.2%) outliers (>3° deviation) in Group B. The severity of the preoperative alignment deformity was a strong predictor for postoperative alignment.

Conclusions:

Using conventional surgical instruments, preoperative measurement of resection thickness of the tibial plateau on radiographs could improve the accuracy of conventional surgical techniques.

Improving tibial component alignment in total knee arthroplasty

PURPOSE

Tibia torsion may influence the accuracy of extramedullary instrumentations in total knee arthroplasty (TKA). This study assessed whether the effect of tibial torsion may be overcome using a surgical technique in which the extramedullary rod is aligned to reference points at the proximal tibia only.

METHODS

A consecutive series of 94 knees that underwent TKA were analyzed. In the first 47 knees (group 1), a standard procedure for tibial component alignment was performed while in the second group of 47 knees, a modified surgical technique was used including the alignment of the extramedullary rod to the reference points at the proximal tibia only (group 2). Lower limb, femoral, and tibial component alignment were measured on postoperative long-leg radiographs.

RESULTS

Femorotibial mechanical axes angles were similar in the two groups. Femoral component alignment also did not differ between the groups. A neutral alignment of the tibial component was achieved in 17 and 34 % of the knees in group 1 and group 2, respectively (p = 0.04). A malalignment of the tibial component >3° was found in 34 % of knees in group 1 compared with 4 % of those in group 2 (p = 0.0001).

CONCLUSIONS

Coronal alignment of the tibial component may improve by setting the extramedullary rod in line with anatomical references in the proximal tibia only. This technique appears to bypass the influence of tibial torsion on the alignment of the extramedullary guide at the distal tibia. The clinical relevance of the study is that using this technique, the rate of malalignment of the tibial component may be reduced compared to a standard technique in which a fixed reference is used at the ankle joint.

Comparison between patient-specific instruments and conventional instruments and computer navigation in total knee arthroplasty: a randomized controlled trial

PURPOSE

The current study investigated the accuracy in achieving proper lower limb alignment and individual component positions after total knee arthroplasty (TKA) with 3 different instrumentation techniques. It was hypothesized that patient-specific instruments (PSI) would achieve more accurate lower limb alignment and component positions compared to conventional instruments (CON).

METHODS

Ninety knees in 81 patients were randomized in 1:1:1 ratio into CON, computer navigation (NAV) and PSI groups to receive TKA. The surgical routines were standardized. The lower limb mechanical axis and individual component positions were assessed on standard radiographs. Tourniquet time, operation time and patients' functional scores were documented.

RESULTS

Conventional instruments and PSI were more likely to result in an excessively flexed femoral component (p = 0.001) compared to NAV. Number of outliers in postoperative lower limb alignment, and other components positions in the coronal and sagittal plane showed no statistically significant difference. The mean tourniquet time and operation time was significantly shorter in CON and PSI groups than NAV group (p < 0.001). Four early complications occurred in the PSI group (p = 0.015). At 3-month follow-up, there was no difference in terms of the knee range of motion and patients' function among the 3 groups.

CONCLUSION

No significant radiological and clinical benefit could be demonstrated in using PSI over CON or NAV in TKA. Routine use of PSI is not recommended because of the extra cost and waiting time.

LEVEL OF EVIDENCE

I.

Significant Incidence of Extra-Articular Tibia Vara Affects Radiological Outcome of Total Knee Arthroplasty

Purpose

To identify and quantify the presence of extra-articular tibia vara that might influence the mechanical axis alignment after total knee arthroplasty (TKA).

Materials and Methods

A total of 48 TKAs in 30 osteoarthritic Indian patients were prospectively evaluated. The hip-knee-ankle angle (HKA), joint line convergence angle, and varus angulation at the femur and tibia were measured from the preoperative and postoperative standing hip-to-ankle radiographs. Four different methods were used to measure the varus angulation at the tibia: metaphyseo-diaphyseal angle (MDA), the angle between the anatomical axis and mechanical axis of the tibia, the angle between the proximal third and distal third of tibia and the angle between the proximal half and distal half of tibia.

Results

Extra-articular tibia vara quantified using MDA had the most positive correlation with HKA. Receiver operating characteristic plotting showed that MDA of >4° predicts abnormal postoperative HKA. Twenty-eight out of 48 knees had MDA of >4°, and 78.6% of these had postoperative HKA under-correction and 21.4% had less than ideal tibial component position.

Conclusions

A significant inherent extra-articular varus angulation best measured using MDA exists in the proximal tibia in osteoarthritic Indian patients undergoing TKA. MDA of >4° is associated with abnormal postoperative HKA. Computer navigation may be useful for achieving ideal correction in such cases.

Total knee arthroplasty with computer-assisted navigation: an analysis of 200 cases

Objective

to evaluate the results from surgery with computer-assisted navigation in cases of total knee arthroplasty.

Method

a total of 196 patients who underwent total knee arthroplasty with computer-assisted navigation were evaluated. The extension and flexion spaces (gaps) were evaluated during the operation and the alignment after the operation was assessed. The Knee Society Score (KSS) questionnaire for assessing patient's function was applied preoperatively and postoperatively after a mean follow-up of 22 months.

Results

in all, 86.7% of the patients presented good alignment of the mechanical axis (less than 3° of varus or valgus in relation to the mechanical axis) and 96.4% of the patients presented balanced flexion and extension gaps. Before the operation, 97% of the patients presented poor or insufficient KSS, but after the operation, 77.6% presented good or excellent KSS.

Conclusion

the navigation system made it possible to achieve aligned and balanced implants, with notable functional improvement among the patients. It was found to be useful in assessing, understanding and improving knowledge in relation to performing arthroplasty procedures.

Analysis on anatomical references to assess the coronal alignment of tibial and femoral cuts in mega prosthetic knee replacement

BACKGROUND

In megaprosthetic knee replacement, surgeons use cutting guides that depend on anatomical references to determine the ideal cutting plane alignment. In this work, we investigated the accuracy of using femoral cortical surfaces and tibial canal portions as the references. The study aims to improve the design and use of the cutting guides.

MATERIALS AND METHODS

Sixty-one knee scanograms of 33 patients (mean age around 20 years) diagnosed with osteogenic sarcoma and undergoing distal femur megaprosthetic surgery were acquired. Angles between the selected anatomical references and axis perpendicular to the ideal cutting plane (anatomical axis for femur and mechanical axis for tibia) were measured for both femur and tibia, in coronal view. The smaller the magnitude of the angles, the better the anatomical reference is.

RESULTS

At the central femoral region, on average, both lateral and medial cortical surfaces give accurate alignment of the ideal cutting plane (0.6° and 0.8°, respectively), with no significant difference (p > 0.01). At the distal region, the lateral cortical surface gives significantly better alignment compared to the medial cortical surface (p < 0.01), but not as accurate (1.4°) as in the central region. For tibia, the central tibial canal gives significantly accurate alignment of the ideal cutting plane (-0.3°) on average, compared to the proximal tibial canal (p < 0.01).

CONCLUSIONS

For a femoral cut, both lateral and medial cortical surfaces are the best anatomical references, but only at the central region. For a tibial cut, the central anatomical axis is the best reference.

LEVEL OF EVIDENCE

IV.

Effects of tibial torsion on distal alignment of extramedullary instrumentation in total knee arthroplasty

BACKGROUND AND PURPOSE

Whether tibial torsion affects the positioning of extramedullary instrumentation and is a possible factor in malalignment of the tibial component in total knee arthroplasty (TKA) is unknown. We assessed the influence of tibial torsion on distal alignment of extramedullary systems for TKA, using the center of the intermalleolar distance as anatomical reference at the ankle joint.

PATIENTS AND METHODS

We analyzed CT scans of knee and ankle joints of 50 patients with knee osteoarthritis (mean age 73 years, 52 legs). The tibial mechanical axis was identified and translated anteriorly at the level of the medial one-third (proximal AP axis 1), at the medial border of the tibial tuberosity (proximal AP axis 2), and at the level of the talar dome (distal AP axis). The center of the intermalleolar distance and the width of the medial and lateral malleolus were calculated. The proximal AP axes 1 and 2 were translated at the level of the ankle joint and any difference between their alignment and the distal AP axis was calculated as angular and linear values.

RESULTS

The center of the ankle joint was located, on average 2 mm medial to that of the intermalleolar distance. The distal AP axis was externally rotated by 18° and 27° compared to the proximal AP axes 1 and 2, respectively. Overall, the center of the ankle joint was shifted laterally by 9-11 mm with respect to the proximal AP tibial axes.

INTERPRETATION

To avoid a varus tibial cut in TKA, extramedullary alignment systems should be aligned more medially at the ankle joint than previously thought, due to the effect of tibial torsion and-to a lesser extent-to the different malleolar width.

Extramedullary versus intramedullary tibial cutting guides in megaprosthetic total knee replacement

BACKGROUND

In a standard total knee replacement, tibial component alignment is a key factor for the long term success of the surgery. The purpose of this study is to compare the accuracy of extramedullary and intramedullary tibial cutting guides used in indigenous and imported implants respectively, in positioning of the tibial components in megaprosthetic knee replacements.

METHODS

A comparative study of the accuracy of extramedullary and intramedullary tibial cutting guides was carried out in 92 megaprosthetic knee replacements for distal femoral tumors. For the proximal tibia cut for tibial component placement, an extramedullary guide was used in 65 patients and an intramedullary guide was used in 27 patients. Tibial component alignment angles were measured in postoperative X-rays with the help of CAD software.

RESULTS

There was more varus placement in coronal plane with extramedullary cutting guide (-1.18 +/- 2.4 degrees) than the intramedullary guide (-0.34 +/- 2.31 degrees) but this did not reach statistical significance. The goal of 90 +/- 2 degrees alignment of tibial component was achieved in 54% of patients in the extramedullary group versus 67% in the intramedullary group. In terms of sagittal plane alignment, extramedullary guide showed less accurate results (2.09 +/- 2.4 degrees) than intramedullary guide (0.50 +/- 3.80 degrees) for tibial component alignment, though 78% of patients were aligned within the goal of 0-5 degrees of tibial slope angle in extramedullary group versus 63% in intramedullary group. The mean error in the measurements due to rotation of the knee during taking the X-rays was less than 0.1 degrees and distribution of the X-rays with the rotation of knee was similar in both the groups.

CONCLUSIONS

Overall, in megaprosthetic knee replacement intramedullary guides gave more accurate results in sagittal plane and exhibited similar variability as of extramedullary guides in coronal plane.

How much tibial resection is required in total knee arthroplasty?

The purpose of our study was to calculate the optimal tibial resection depth in total knee arthroplasty. The data from 464 navigated total knee arthroplasties were analysed. An implant with a minimum insert thickness of 8 mm was used. Data regarding leg axis, joint line, insert thickness and tibial resection depth were recorded by the navigation device. An algorithm was developed to calculate the optimal tibial resection depth. The required tibial resection significantly correlates with the preoperative leg axis (p < 0.001). In valgus deformities the required resection depth averaged 5.1 mm and was significantly reduced compared to knees with a neutral leg axis (6.8 mm, p < 0.001) and varus deformities (8.0 mm, p < 0.001). Manufacturers recommend undercutting the high side of the tibial plateau to the depth of the thinnest insert available. However, our study demonstrates that in valgus deformities a reduced tibial resection depth is preferable. Hence, unnecessary bone loss can be avoided.

Navigation knee replacement

Total knee replacement (TKR) achieves an immediate and exceptional restoration in the quality of life that is comparable only to a few other procedures. It has been suggested that the most common cause of revision TKR is error in surgical technique, from malpositioning of the components which results in a poorer post-operative outcome. Based on the theoretical assumption that the use of computer-assisted systems (CAS) in TKRs may improve implant alignment and thus implant longevity, the use of this technology is becoming increasingly popular. This article (a) reviews whether computer-assisted TKR (CASTKR) results in improved prosthesis alignment compared with the conventional technique, (b) assesses the functional and clinical outcomes of CASTKR and (c) evaluates the cost-effectiveness of using this technology.

Assessment and validation of CT scanogram to compare per-operative and post-operative mechanical axis after navigated total knee replacement

Our objective was to assess and validate low-dose computed tomography (CT) scanogram as a post-operative imaging modality to measure the mechanical axis after navigated total knee replacement. A prospective study was performed to compare intra-operative and post-operative mechanical axis after navigated total knee replacements. All consecutive patients who underwent navigated total knee replacement between May and December 2006 were included. The intra-operative final axis was recorded, and post-operatively a CT scanogram of lower limbs was performed. The mechanical axis was measured and compared against the intra-operative measurement. There were 15 patients ranging in age from 57 to 80 (average 70) years. The average final intra-operative axis was 0.56 degrees varus (4 degrees varus to 1.5 degrees valgus) and post-operative CT scanogram axis was 0.52 degrees varus (3.1 degrees varus to 1.8 degrees valgus). The average deviation from final axes to CT scanogram axes was 0.12 degrees valgus with a correlation coefficient of 0.9. Our study suggests that CT scanogram is an imaging modality with reasonable accuracy for measuring mechanical axis despite significantly low radiation. It also confirms a high level of correlation between intra-operative and post-operative mechanical axis after navigated total knee replacement.