Total knee arthroplasty in valgus knees: predictive preoperative parameters influencing a constrained design selection

Long-term results (after a mean 11.3years, and up to 22years, of follow-up) of the Legacy Constrained Condylar Knee (LCCK™) in primary total knee arthroplasty

INTRODUCTION

The use of a sliding prosthesis in total knee arthroplasty (TKA) with increased stress is an intermediate solution in primary surgery, between posteriorly stabilized prostheses and hinged prostheses, in cases of ligamentous laxity and/or loss of bone substance. Favorable results have been reported in the medium term but to our knowledge, this type of prosthesis has not been evaluated in Europe beyond 10 years of follow-up. We therefore conducted a retrospective study in order to carry out: 1) the study of the survival of the Legacy Constrained Condylar Knee (LCCK™) prosthesis in primary surgery, 2) the analysis of complications, functional scores and radiographic data, 3) the analysis of the link between the diaphyseal filling rate and prosthetic loosening.

HYPOTHESIS

The LCCK™ sliding prosthesis with increased constraint has equivalent long-term survival and clinical results to standard posteriorly stabilized TKA and superior to hinged TKA.

MATERIAL AND METHOD

A retrospective series of 141 LCCK™ implanted in 134 patients between 1997 and 2010 was analyzed. Survival was assessed with censoring through an evaluation of partial or total revision of the implants. The functional results were evaluated using the IKS and Oxford 12 scores. Data regarding the Canal Fill Ratio (CFR) and the presence of pathological periprosthetic lines were also collected.

RESULTS

The average follow-up was 11.3±5.3years with a maximum follow-up of 22.7years. Survival at 20years was 90.8% [95% CI: 83.7-95.7]. The rate of early complications was 13.5% (19/141), predominantly comprised of venous thrombosis (6/141), hematomas (3/141 including two requiring surgical drainage), stiffness (3/141) and early infections (3/141). The rate of late complications was 17% (24/141), led by stiffness (4.4%; 6/141), infections (2.9%; 4/141) and hardware failure (2. 2%; 3/141). Ten of the 141 patients (7.1%) had LCCK failure, including 3 (2.1%) for stiffness, 3 (2.1%) for hardware failure, 2 (1.4%) for infection, 1 (0.7%) for laxity and 1 (0.7%) for a periprosthetic fracture. No aseptic loosening was found. The total IKS score went from 65 [0-116] to 143 [79-200] at follow-up, the IKS knee score went from 30 [0-66] to 85 [44-100], and the IKS function score went from 35 [0-70] to 57 [0-100]. The Oxford score went from 14 [2-25] to 34 [15-48] at follow-up. Only two patients (1.4%) presented with a partial periprosthetic line. The tibial CFR was 0.81 and the femoral CFR was 0.76. The influence of the CFR could not be analyzed due to the absence of loosening.

DISCUSSION

The LCCK™ prosthesis in primary surgery has good medium-term survival, a significant improvement in functional scores and a complication rate comparable to posteriorly stabilized prostheses. The complication rate is lower than that of hinged prostheses.

LEVEL OF EVIDENCE

IV; single-center retrospective study.

Knee valgus deformity and lateral bone defects affect the function of superficial medial collateral ligament: A finite element analysis

Purpose

The superficial medial collateral ligament (sMCL) is the primary restraint to valgus laxity of the knee, which is one of the significant indicators of implant selection in valgus knee. Our purpose is to explore the influence of knee valgus deformity and lateral bone defects in the function of sMCL.

Methods

the right knee joint of a healthy male volunteer was subjected to CT and MRI scans. The scanned data were imported into Mimics, Geomagic, Solidworks and Ansys software to establish a three-dimensional finite element model of the human knee joint. Femorotibial angle (FTA)5°,10°,15°,20°,25°,30°,35° and lateral bone defect 0,0.5,1,1.5,2 cm are controlled in Solidworks. Tensile test in vitro of maximum load on sMCL was simulated in Ansys.

Results

The peak stress of sMCL is raising with valgus deformity while there is no lateral defect. Increasing lateral bone defect can lessen the augmentation of the stress of sMCL caused by the valgus deformity. The peak stress of sMCL when it is in maximum load is 35.252 MPa. While valgus 35°, the peak stress of sMCL exceeds the value, with or without bone defect; the same is true for the valgus 30° with 0, 0.5, 1 cm bone defect and valgus 25° without defect.

Conclusion

Our findings allow for preoperative evaluation of sMCL function in the valgus knee, which would play an instructive role to some extent for implant selection in total knee arthroplasty.

Is lateral femoral condyle hypoplasia a feature of genu valgum? A morphological computed tomography study of 200 knees

BACKGROUND

Young surgeons are taught that genu valgum deformity is associated with hypoplasia of the lateral femoral condyle, despite the absence of supporting evidence. The objective of this study was to determine whether the lateral condyle was hypoplastic in genu valgum, by assessing the morphological features of the distal femur and their variations according to the severity of the coronal deformity.

HYPOTHESIS

The lateral femoral condyle is not hypoplastic in genu valgum deformity.

MATERIAL AND METHODS

The 200 included patients treated by unilateral total knee arthroplasty were divided into five groups based on their preoperative hip-knee-ankle (HKA) angle. The HKA angle, valgus cut angle (VCA), and anatomical lateral distal femoral angle (aLDFA) were measured on long-leg radiographs. Computed tomography images were then used to measure the medial and lateral anterior-posterior condylar lengths (mAPCL and lAPCL) and condylar thicknesses (mCT and lCT), distal femoral torsion (DFT), medial and lateral posterior condylar heights (mPCH and lPCH), and medial and lateral condylar volumes (mCV and lCV).

RESULTS

No significant differences were demonstrated across the five mechanical-axis groups for mAPCL, lAPCL, mCT, lCT, mPCH, or lPCH. The groups differed significantly regarding the VCA (p<0.0001), aLDFA (p<0.0001), DFT (p<0.0001), and mCV/lCV ratio (p<0.0001). VCA and aLDFA were smaller when the valgus exceeded 10°. DFT was similar in all varus knees (2.2°-2.6°) but significantly greater for knees with moderate (4.0°) or severe (6.2°) valgus. Finally, lCV was greater than mCV in valgus knees compared to varus knees.

CONCLUSION

The presence of lateral condyle hypoplasia in knees with genu valgum seems open to question. Apparent hypoplasia noted during the standard physical examination may be chiefly ascribable to distal valgus of the femoral epiphysis in the coronal plane and, with the knee flexed, to distal epiphyseal torsion, whose severity increases with the degree of valgus deformity. These considerations should be taken into account when performing distal femoral cuts for TKA, to ensure the restoration of normal anatomy in patients with genu valgus.

LEVEL OF EVIDENCE

IV.

Valgus arthritic knees can be classified into nine phenotypes

PURPOSE

It is not shown whether anatomical variations exist in valgus arthritic limbs as to support individualized component and limb alignment. The null hypothesis was that there was no phenotypic variation of coronal femoro-tibial morphology in valgus knees. The aim was to determine whether distinct phenotypes of valgus knees could be identified to help surgical planning and classifying valgus knees for outcome studies.

METHODS

Full-leg weight-bearing radiographs of 233 knees (182 preoperative; 51 of contralateral arthritic knee) were measured for HKA (hip-knee-ankle angle), VCA (valgus correction angle), mLDFA (lateral mechanical distal femoral angle), aLDFA (lateral anatomical distal femoral angle), MPTA (medial proximal tibial angle), MNSA (medial neck shaft angle), TAMA (angle between tibial mechanical and anatomical axes), and TBA (tibial bowing angle).

RESULTS

Nine phenotypes were identified encompassing all 233 knees which could be clubbed into 4 broad types. Type 1 Neutral knees (12.5%) had almost normal values (mean VCA 5.3°, mLDFA 86.9°, aLDFA 81.1°). Type 2 'Intra-articular valgus' (22.7%) showed lateral compartment bone loss (mean mLDFA 83.9°; MPTA 90.2°). Type 3 'Extra-articular valgus' (35.2%) had extra-articular deformity: 3a showed valgus femoral bowing (mean VCA 2.7°); 3b valgus tibial bowing; 3c showed valgus tibial bowing with lateral femoral condyle wear (mean mLDFA 84.3°). Type 4 'Varus' type (29.6%) had features of varus knees: 4a had varus femoral bowing (VCA 8.3°); distal femur in 4b was akin to varus knees (mean mLDFA 89.3°) with lateral tibial bone loss (mean MPTA 91.2°). 4c had varus tibial bowing and deficient lateral femoral condyle (mLDFA 83.7°). 4d had varus tibial bowing and lateral tibial bone loss (mean MPTA 89.8°).

CONCLUSIONS

The study identified four broad groups of valgus arthritic knees with nine phenotypes based on coronal plane variations in femoro-tibial morphology. This study may be of value in planning and performing corrective osteotomies, and planning the optimal position of femoral and tibial components in unicompartmental and total knee arthroplasty. The classification presented in this study may aid in categorizing valgus knees for outcome studies.

LEVEL OF EVIDENCE

IV.

Improved surgical procedure of primary constrained total knee arthroplasty which enables use of the femoral diaphyseal straight extension stem

Background

In performing primary constrained total knee arthroplasties (TKA) to imbalanced knees, the offset stem is sometimes compelled to use, although this is associated with surgical difficulties. We developed a modified procedure which might be able to fit the anteroposterior (AP) and mediolateral (ML) position of the femoral component simultaneously with the straight stem. Purposes of this study were to evaluate usefulness of the modified procedure both in computer simulations and actual surgeries.

Methods

We included 32 knees that had undergone primary TKA using constrained implants because of the coronal imbalance. In the component-first procedure, the distal femur was prepared to fit the AP and ML position of the femoral component simultaneously at first, as in primary TKA. Finally, the stem hole is created based on the femoral component position (the component-first procedure). The femoral component and extension stem were simulated using the three-dimensional planning software (ZedKnee) following the component-first procedure. We investigated the suitability of the straight stem through computer simulation and evaluation of actual surgeries. Clinical and radiographical outcomes were also evaluated at the latest follow-up.

Results

The component-first procedure enabled the AP and ML position of the femoral component to be fitted simultaneously with the straight stem in simulations and actual surgeries in all cases. The stem diameter was not significantly different between simulations and actual surgeries (13.9 and 13.7 mm on average, respectively, p = 0.479) and almost similar from intraclass correlation coefficient analysis (kappa value 0.790). Clinical and radiographical outcomes were almost similar to primary TKA cases and there was no case of component loosening, cortical bone hypertrophy around the stem and stem-tip pain.

Conclusions

Our improved surgical procedure may facilitate use of the constrained implant for more cases of primary TKA in imbalanced knees without the usual surgical difficulties.

Trial registration

Retrospectively registered.

The use of mobile bearing TKA in valgus deformities - A clinical study

BACKGROUND

The number of patients presenting valgus deformities undergoing total knee arthroplasty (TKA) represents approximately 10% of the total number of TKAs performed: the presence of valgus deformity requires the implant to have proper alignment, stability and balance to achieve successful clinical outcomes, especially for knees with high coronal deformities, but these have proven to be difficult goals to achieve and therefore the use of constrained prostheses is often recommended for these cases. However, even though the use of unconstrained mobile bearing for severe knee deformities is rare, it has been shown to give successful outcomes and therefore the aim of this study is to evaluate whether this surgical technique can achieve satisfactory clinical results and correct alignment, as well as good patient satisfaction.

METHODS

This study presents the results of 69 TKA performed with cemented mobile bearing implants by a single surgeon on knee affected by valgus deformities. Asymmetric inserts were adopted for all the implants and an alignment surgical tool, dedicated for valgus patients, was used during the operation. Angles of valgus, WOMAC surveys and Numeric Rating Scale for pain were recorded to evaluate the results of the operations.

RESULTS

A total of 67 pre-op WOMAC questionnaire surveys were collected, with the mean result of this evaluation being 15.9 points. The Numeric Rating Scale for pain had an average of 2.2 for 68 tests. The deformities were corrected from a mean total preoperative valgus angle of 12.5° to a postoperative valgus deformity average of 0.6°. During follow-up, only one patient had serious complications due to the rupture of the extensor apparatus following a domestic accident involving falling. Further 10 patients have mild complications related to injuries such as pain of varying intensity, burning, or swelling of the knee. The level of satisfaction from 0 to 10 (0 not at all satisfied and 10 perfectly satisfied) had an average score of 7.7.

CONCLUSIONS

The surgical approach presented, involving a less constrained model if compared to the ones usually chosen, allowed to achieve correct alignment and high patient satisfaction using mobile bearing implants on valgus knee deformities; further patient follow-up will be performed to evaluate long-term outcomes, but the results achieved already represent a significative finding.

Mid-term results of complex primary total knee arthroplasty using a rotating-hinge implant

BACKGROUND

The indications and outcomes of semi- or fully-constrained knee implants in primary total knee arthroplasty (TKA) are still controversially discussed. The present study aims to evaluate the mid-term results and complications of a modular/non-modular rotating-hinge implant in complex primary TKA.

METHODS

Eighty-two patients (86 knees) following primary TKA were retrospectively evaluated with a mean follow-up of 63 months. The functional outcome was assessed using the American Knee Society Score (AKSS) and the Oxford Knee Score (OKS). A Visual Analog Scale (VAS) was used to determine pain levels. Implant survival and reoperation rateswere estimated using competing risk analysis. Cox regression analysis wasperformed to evaluate the influence of modularity on implant survival.

RESULTS

The survival rate with the endpoint implant revision was 90% (95 %CI:83-98%) and the survival rate with the endpoint all reoperations was 84% (95 %CI:75-94%) at 7 years. The AKSS improved significantly from 24 (SD 14.9, range:0-69) preoperatively to 83 (SD 14.3, range:57-100) postoperatively (p < 0.001); functional AKSS improved significantly from 27 (SD 24.3, range:0-100) to 46 (SD: 32.9, range 0-100) (p = 0.003), and OKS from 19 (SD: 8.3, range:5-43) to 29 (SD: 10.7, range:6-48), respectively (p < 0.0001). VAS decreased significantly from 8 (SD: 2.6, range:0-10) preoperatively to 3 (SD: 2.9, range:0-9) postoperatively (p < 0.0001). There was no significant influence of modularity on revision rates comparing modular to non-modular implants (p = 0.072).

CONCLUSIONS

The present rotating-hinge implant provides substantial improvement in function and reduction of pain with good implant survival in the mid-term. Modularity was not associated with higher rates of revision.

Primary complex total knee arthroplasty with severe varus deformity and large bone defects: mid-term results of a consecutive series treated with primary implants

INTRODUCTION

In recent years, the use of constrained implants in complex primary TKA has gained popularity since these implants may better and more easily address severe instability present in complex primary cases (CPC). However, the need for a constrained TKA in CPC is controversial. We hypothesized that a standard TKA may be successful in most of CPC and that an intraoperative switching to a constrained device is rarely need even in the presence of severe instability and bone loss.

MATERIALS AND METHODS

A consecutive series of 24 CPC (28 knees) were analysed retrospectively. Inclusion criteria were a femoro-tibial angle > 12° and bone defect of grade 2-3 (group 1). Forty-eight patients (52 knees) were analysed as controls (group 2). Patients were followed up clinically and radiographically up to a minimum of 5 years.

RESULTS

In group 1, a PS was used in 24 knees and a CR in 4. In no patient, a CCK or RHK was implanted. Bone defect was treated with bone cement plus cortical screws in 15 knees (53.5%), a medial wedge in 8 (28.5%), a medial wedge plus bone grafting with cancellous screws in 5 (17.8%). Metaphyseal sleeve or cone was not used. At the last follow-up, no significant difference was found in the clinical scores between the 2 groups.

CONCLUSION

In CPC with marked varus deformity, instability and bone loss, the use of primary TKA is associated with a clinical outcome comparable to standard cases. Ligamentous balancing may be addressed using primary implants and simple cost-effective techniques may be used to manage an extensive bone loss. In most CPC, an intraoperative switching to a constrained device is not necessary.

Rotating-hinge prosthesis for aseptic revision knee arthroplasty: A multicentre retrospective study of 127 cases with a mean follow-up of five years

BACKGROUND

The use of third-generation rotating-hinge knee prostheses has increased considerably in recent years. The more anatomical design of these prostheses, together with their controlled rotation system that reduces constraints generated by the single degree of liberty, have produced better outcomes. The objective of this study was to evaluate the clinical and radiological outcomes of revision knee arthroplasty for aseptic failure using rotating-hinge prostheses.

HYPOTHESIS

The rotating-hinge knee prostheses currently used in France provide significant improvements in function and self-sufficiency of patients undergoing revision knee arthroplasty, with outcomes comparable to those reported with constrained condylar knees.

MATERIAL AND METHODS

A multicentre retrospective study was conducted in 17 centres, under the auspices of the SoFCOT. The cohort consisted of 127 patients (127 knees) operated on before 2013. The main reasons for knee revision were aseptic loosening, major instability, mechanical failure, and extensor apparatus failure. Function and self-sufficiency were assessed using the International Knee Society (IKS) score and the Devane score, respectively. Survival was defined with all-cause surgical revision as the end point.

RESULTS

Mean follow-up was 67.3±11.8 months (range, 13-180 months). Significant improvements (p<0.001) were seen in the total IKS score (+42 points), the IKS function score (+12 points), and the knee IKS score (+30 points). Paradoxically, the Devane score decreased by 0.44 point. The 5-year survival rate was 77% (95% confidence interval, 0.70-0.85). Postoperative complications developed in 29% of patients (infection, n=12; aseptic loosening, n=11; and fracture, n=7).

DISCUSSION

Rotating-hinge prostheses provide satisfactory outcomes of knee arthroplasty revision and remain an effective option for complex cases, confirming our working hypothesis. Self-sufficiency diminishes slightly. The long-term outcomes obtained using rotating-hinge prostheses are, however, less satisfactory than those observed with constrained condylar knees for aseptic TKA revision, and the complication rate is higher, although the population and local circumstances are different. Discernment is therefore in order when determining the indications of rotating-hinge prostheses.

LEVEL OF EVIDENCE

IV; retrospective cohort study.

When to Use a Condylar Constrained Insert in Non-Stemmed Posterior-Stabilized Total Knee Arthroplasty

Backgroud

The constrained insert with non-stemmed tibial and femoral components can be used in the modern total knee arthroplasty (TKA) when soft-tissue balance and adequate stability from a posterior-stabilized (PS) insert cannot be achieved. This study aimed to identify the prevalence and predictive factors associated with the constrained insert use during primary TKA for varus deformity.

Methods

From August 2016 to March 2019, 554 primary TKAs were consecutively performed by one surgeon. The choice of using a conventional PS polyethylene insert versus a constrained insert was made by the surgeon, depending on the stability detected after an attempt to balance the soft tissue. The decision to convert to a constrained liner was made if the ligament could not be balanced, if flexion-extension gaps were mismatched, or if the varus-valgus opening was 3 mm or more when varus and valgus stress tests at 0° were applied. We retrospectively investigated the preoperative, intraoperative, and postoperative factors associated with the constrained insert use. Multiple logistic regression analysis was used to identify predictive factors of constrained insert use, and a receiver operating characteristic curve analysis was used to pinpoint a cutoff value of tibiofemoral varus angle.

Results

Constrained inserts were used in 130 of 497 varus knees (26.1%). A multivariate analysis revealed that the factors associated with an increased adjusted risk of constrained insert use included preoperative severe varus deformity (odds ratio [OR], 5.78; 95% confidence interval [CI], 2.75–12.16; p < 0.001) and severe release of soft tissue through the superficial medial collateral ligament (OR, 6.38; 95% CI, 2.94–13.85; p < 0.001). A preoperative anatomic tibiofemoral varus angle of > 19.8° was associated with the use of a constrained articulation with an area under the curve of 0.7 (95% CI, 0.4–0.8).

Conclusions

Prevalence of 26.1% for constrained insert use was found in this study. Preoperative anatomic tibiofemoral varus angle of > 19.8° and severe release of soft tissue through the superficial medial collateral ligament were associated with the use of a constrained articulation. The findings from this study will help surgeons to improve efficiency of surgical sequence planning and provide counseling to patients regarding the associated cost.

Total knee arthroplasty with the least-constrained implant possible for type II valgus knee > 20°: a 3–14 years’ follow-up

Objective

To estimate the midterm outcome of primary total knee arthroplasty for severe valgus deformity using selective release of tight lateral structures and the least-constrained implant.

Methods

We performed total knee arthroplasty on 65 consecutive type II knees with valgus deformity> 20°. Surgery was done via a medial parapatellar approach. Conventional bone cutting was done with selective lateral soft tissue release, and the least-constrained total knee prosthesis possible was used. Posterior stabilized implants were employed in most knees, except for three knees that required the implantation of constrained condylar knee prostheses. The average duration of follow-up lasted for 10.5 years.

Results

Preoperatively, average valgus was 30.6°, and average range of motion was 43.7° (range, 0–80°). Postoperatively, average valgus was 7.3° and average range of motion was 110.6° (range, 80–130°). The lateral collateral ligament and iliotibial band were released in all knees, and release of the popliteus tendon was required in two knees. Stable flexion and extension gaps were achieved in most cases, except for two that had medial side instability. Follow-up showed that stability was maintained.

Conclusions

This surgical technique combined selective lateral soft tissue release with use of the least-constrained implant possible and was effective for severe valgus deformities of the knee, with good clinical results.

Coronal plane laxity of valgus osteoarthritic knee

Balanced soft tissues are important to total knee arthroplasty (TKA) outcomes. Surgical algorithms for balancing are potentially varied in varus and valgus osteoarthritic (OA) knees. While coronal plane varus knee laxity has been documented, no study has objectively defined the medial and lateral laxity of the valgus OA knee. The lower limb was manipulated at the time of TKA using computer navigation, prior to surgical releases, to allow the limb weight-bearing axis to pass through the knee center in maximum extension, 20° and 90° of flexion. The hip-knee-ankle-angle was documented at this position. Coronal plane laxity was then measured in 30 valgus (7.9 ± 4.0°) knees as medial and lateral displacement from this point and compared to published values for healthy subjects. In maximum knee extension, lateral contracture was present in 26.6% (8/30) of subjects, and abnormally lax medial tissue was present in 46.6% (14/30). Six patterns of medial versus lateral laxity were documented in maximum extension. In maximum knee extension, mean medial laxity was 7.1° (±3.8°) compared to 2.7° (±2.7°) laterally. In 20° of knee flexion, mean medial laxity was 8.5° (±3.5°) compared to 3.0° (±2.6°) laterally. In 90° of knee flexion, mean medial laxity was 3.7° (±1.3°) and 7.5° (±3.0°) laterally. A highly significant difference ( p < 0.0001) in mean laxity was demonstrated when comparing medial versus lateral values at each measurement angle and for medial versus medial and lateral versus lateral values for maximum extension and 90° of flexion. The valgus knee at the time of TKA demonstrates significant preoperative mediolateral and flexion-extension imbalance. In maximum extension, medial tissue is significantly laxer whereas in flexion this reverses and the lateral tissue is significantly laxer. We documented more patterns of medial and lateral laxity in maximum extension than advocated in prior subjective grading systems. These findings demonstrate the challenges of valgus OA knee balancing during TKA but provide, for the first time, objective measures for the starting point of this process.

Semi-constrained posterior stabilized total knee arthroplasty reproduces natural deep knee bending kinematics

BACKGROUND

The Flexible Nichidai Knee Posterior Stabilized (FNK-PS) system was designed to provide relatively high varus-valgus stabilities without the stem extensions to patients with severe knee joint disorders. This is a combination of a large tibial post and high femoral cam adapted to a PS system. The aim of our study was to analyze the in vivo two-dimensional/three-dimensional registration kinematics of the FNK PS-total knee arthroplasty (TKA) system during deep knee bending.

METHODS

Nineteen knees from 15 total knee arthroplasty (TKA) patients who were able to squat with enough knee flexion were selected. During deep knee bending under weight bearing (WB) and non-weight bearing (NWB) conditions, we quantified range of motion, axial rotation, femoral anteroposterior translation, and post-cam engagement angle.

RESULTS

The maximum-flexion was significantly different between the two conditions. The mean axial femoral external rotation was 4.8° and 6.2° under WB and NWB conditions, respectively, at 120° flexion. Anteroposterior translation based on bicondylar posterior roll-back patterns was noted with increasing knee flexion. Both the medial and lateral femoral aspects were significantly more posterior during early to mid-flexion. Initial post-cam engagement occurred significantly earlier during flexion under NWB than under WB conditions. Under WB, the timing of the post-cam engagement correlated with the maximum flexion .

CONCLUSIONS

The kinematics of the semi-constrained PS system reproducibly exhibited a mild external rotation with smooth posterior roll-back. This was assisted by the engagement of the large tibial post and high femoral cam during the early phase of flexion.

Total knee replacement on more than 20° valgus: A case control study

INTRODUCTION

Lower-limb valgus deformity exceeding 20° is a particular case, with few publications assessing the impact of the severity of the valgus. The present retrospective case control study compared a series of>20° valgus versus a series of 10-20° valgus, assessing (1) operative data [approach, type of total knee replacement (TKR)], (2) complications and implant survival, and (3) clinical and radiological results.

HYPOTHESIS

Severe valgus deformity requires TKR with greater constraint, incurring a higher rate of complications and poorer implant survival.

MATERIAL AND METHOD

A multicenter retrospective study for the period January 2006 to December 2010 included 53 patients, with a mean age of 72±10 years, presenting>20° valgus. The study series was matched for age and gender with a series of 53 cases of 10-20° valgus. Convexity laxity was greater in the>20° group (p=0.004).

RESULTS

There was no significant inter-group difference in approach (p=0.13). Greater constraint was more frequent in the>20° group (7/53 versus 1/53; p=0.03), independently of convexity laxity or Krackow grade (p=0.14). There were 7 complications (13.2%) in the>20° group and 7 in the 10-20° group (NS). Eight-year survivorship was 95.12% in the>20° group and 94.9% in the 10-20° group (p=0.63). There were no significant differences in Oxford score (p=0.30) or HKA angle (p=0.78) at last follow-up.

CONCLUSION

The study hypothesis was partially confirmed: greater constraint was more frequent in>20° valgus. The number of complications was low, and survival was identical to that of a control group with less severe deformity.

LEVEL OF EVIDENCE

III, retrospectivecase controlstudy.

Increased valgus laxity in flexion with greater tibial resection depth following total knee arthroplasty

PURPOSE

Soft tissue balancing is of central importance to outcome following total knee arthroplasty (TKA). However, there are lack of data analysing the effect of tibial bone cut thickness on valgus laxity. A cadaveric study was undertaken to assess the biomechanical consequences of tibial resection depth on through range knee joint valgus stability. We aimed to establish a maximum tibial resection depth, beyond which medial collateral ligament balancing becomes challenging, and a constrained implant should be considered.

METHODS

Eleven cadaveric specimens were included for analysis. The biomechanical effects of increasing tibial resection were studied, with bone cuts made at 6, 10, 14, 18 and 24 mm from the lateral tibial articular surface. A computer navigation system was used to perform the tibial resection and to measure the valgus laxity resulting from a torque of 10 Nm. Measurements were taken in four knee positions: 0° or extension, 30°, 60° and 90° of flexion. Intra-observer reliability was assessed. A minimum sample size of eight cadavers was necessary. Statistical analysis was performed using a nonparametric Spearman's ranking correlation matrix at the different stages: in extension, at 30°, 60° and 90° of knee flexion. Significance was set at p < 0.05.

RESULTS

There was no macroscopic injury to the dMCL or sMCL in any of the specimens during tibial resection. There was no significant correlation found between the degree of valgus laxity and the thickness of the tibial cut with the knee in extension. There was a statistically significant correlation between valgus laxity and the thickness of the tibial cut in all other knee flexion positions: 30° (p < 0.0001), 60° (p < 0.001) and 90° (p < 0.0001). We identified greater than 5° of valgus laxity, at 90° of knee flexion, after a tibial resection of 14 mm.

CONCLUSION

Increased tibial resection depth is associated with significantly greater valgus laxity when tested in positions from 30° to 90° of flexion, despite stability in extension. Greater than 5° of laxity was identified with a tibial resection of 14 mm. When a tibial bone cut of 14 mm or greater is necessary, as may occur with severe preoperative coronal plane deformity, it is recommended to consider the use of a constrained knee prosthesis.

Medial and lateral gap laxity differential in computer-assisted kinematic total knee arthroplasty

Aims

The results of kinematic total knee arthroplasty (KTKA) have been reported in terms of limb and component alignment parameters but not in terms of gap laxities and differentials. In kinematic alignment (KA), balance should reflect the asymmetrical balance of the normal knee, not the classic rectangular flexion and extension gaps sought with gap-balanced mechanical axis total knee arthroplasty (MATKA). This paper aims to address the following questions: 1) what factors determine coronal joint congruence as measured on standing radiographs?; 2) is flexion gap asymmetry produced with KA?; 3) does lateral flexion gap laxity affect outcomes?; 4) is lateral flexion gap laxity associated with lateral extension gap laxity?; and 5) can consistent ligament balance be produced without releases?

Patients and Methods

A total of 192 KTKAs completed by a single surgeon using a computer-assisted technique were followed for a mean of 3.5 years (2 to 5). There were 116 male patients (60%) and 76 female patients (40%) with a mean age of 65 years (48 to 88). Outcome measures included intraoperative gap laxity measurements and component positions, as well as joint angles from postoperative three-foot standing radiographs. Patient-reported outcome measures (PROMs) were analyzed in terms of alignment and balance: EuroQol (EQ)-5D visual analogue scale (VAS), Knee Injury and Osteoarthritis Outcome Score (KOOS), KOOS Joint Replacement (JR), and Oxford Knee Score (OKS).

Results

Postoperative limb alignment did not affect outcomes. The standing hip-knee-ankle (HKA) angle was the sole positive predictor of the joint line convergence angle (JLCA) (p < 0.001). Increasing lateral flexion gap laxity was consistently associated with better outcomes. Lateral flexion gap laxity did not correlate with HKA angle, the JLCA, or lateral extension gap laxity. Minor releases were required in one third of cases.

Conclusion

The standing HKA angle is the primary determinant of the JLCA in KTKA. A rectangular flexion gap is produced in only 11% of cases. Lateral flexion gap laxity is consistently associated with better outcomes and does not affect balance in extension. Minor releases are sometimes required as well, particularly in limbs with larger preoperative deformities. Cite this article: Bone Joint J 2019;101-B:331–339.

Midlevel Constraint Without Stem Extensions in Primary Total Knee Arthroplasty Provides Stability Without Compromising Fixation

BACKGROUND

Many total knee arthroplasty (TKA) systems allow for so-called midlevel constraint (MLC) articular bearings that can be used with primary implants. The purpose of this study is to report the early outcomes with MLC bearings in primary TKA.

MATERIALS/METHODS

From December 2005 to June 2015, minimum 2-year follow-up was available on 96 patients (103 TKA) who underwent primary TKA with an MLC bearing using the Vanguard Total Knee System. Outcomes included pain, Knee Society clinical and functional score, range of motion, and need for revision.

RESULTS

Mean follow-up was 5 years (range, 2-11 years). Range of motion improved from 103 to 113. Knee Society clinical and function scores improved from 28 and 43 to 88 and 62, respectively. There were 10 manipulations (9.9%). There were no failures for aseptic loosening of any components; however, 10% of patients were lost to follow-up. There were 3 revisions (3%): 1 patellar tendon rupture, 1 open lysis of adhesions for stiffness, and 1 2-stage treatment of infection.

CONCLUSION

In cases of intraoperative medial collateral ligament incompetence, severe deformity, or valgus deformity requiring release of the lateral collateral ligament, the use of MLC showed good survivorship with no cases of aseptic loosening or instability.

Knee instability as the primary cause of failure following Total Knee Arthroplasty (TKA): A systematic review on the patient, surgical and implant characteristics of revised TKA patients

BACKGROUND

The aim of this review was to systematically assess the current evidence available regarding knee instability after TKA to identify time to failure between primary and revision TKA. In addition, we considered the patient, surgical and implant characteristics of primary TKA patients revised for knee instability, and investigated methods used for knee instability diagnosis.

METHODS

A systematic search of six databases and the unpublished literature was performed. Studies referring to instability in post-operative primary TKA patients, reporting on revision TKA due to instability, and published or available between 2005 to 30-Mar-2015 were eligible for inclusion. Quantitative data for continuous variables were pooled in statistical meta-analyses.

RESULTS

A total of 1841 unique studies were identified, 42 of which met the selection criteria and a total of 22 studies included in the review. Time to failure between primary and revision TKA was 44.7months (95% CI [33.8, 55.7]), and the weighted mean age at time of revision surgery was 67.6years (95% CI [65.38, 69.75]). A gender distribution was identified, with approximately 16.4% more females revised for instability, however this was unable to be corrected for the baseline population. The majority of studies used a combination of radiographic and clinical testing to diagnose knee instability.

CONCLUSION

Research on knee instability following primary TKA reported early failure and subsequent revision knee surgery. The need for revision due to instability was frequently reported in a younger patient cohort and most commonly in female TKA patients. Early revision at a younger age highlights the severe implications of an unstable knee.

An in vitro analysis of medial structures and a medial soft tissue reconstruction in a constrained condylar total knee arthroplasty

PURPOSE

The aim of this study was to quantify the medial soft tissue contributions to stability following constrained condylar (CC) total knee arthroplasty (TKA) and determine whether a medial reconstruction could restore stability to a soft tissue-deficient, CC-TKA knee.

METHODS

Eight cadaveric knees were mounted in a robotic system and tested at 0°, 30°, 60°, and 90° of flexion with ±50 N anterior-posterior force, ±8 Nm varus-valgus, and ±5 Nm internal-external torque. The deep and superficial medial collateral ligaments (dMCL, sMCL) and posteromedial capsule (PMC) were transected and their relative contributions to stabilising the applied loads were quantified. After complete medial soft tissue transection, a reconstruction using a semitendinosus tendon graft was performed, and the effect on kinematic behaviour under equivocal conditions was measured.

RESULTS

In the CC-TKA knee, the sMCL was the major medial restraint in anterior drawer, internal-external, and valgus rotation. No significant differences were found between the rotational laxities of the reconstructed knee to the pre-deficient state for the arc of motion examined. The relative contribution of the reconstruction was higher in valgus rotation at 60° than the sMCL; otherwise, the contribution of the reconstruction was similar to that of the sMCL.

CONCLUSION

There is contention whether a CC-TKA can function with medial deficiency or more constraint is required. This work has shown that a CC-TKA may not provide enough stability with an absent sMCL. However, in such cases, combining the CC-TKA with a medial soft tissue reconstruction may be considered as an alternative to a hinged implant.

Concurrent femoral and tibial osteotomies versus soft tissue balance in total knee arthroplasty: A technical case report

This case report outlines some of the challenges as well as limitations in correction of osteoarthritis of the knee in combination with extra-articular deformities,and provides a novel and straightforward surgical solution in overcoming these challenges. We describe the case of a 37-year-old male who suffered from advanced bilateral tri-compartmental knee arthritis due to untreated bloodstream-sourced osteomyelitis after birth. Radiographs and surgery confirmed extremely severe deformities. We performed two different surgical techniques in order to correct extra-articular deformities (one-stage approach of concurrent tibial and femoral osteotomy and total knee arthroplasty on one side, and soft tissue balancing with "pie-crusting technique" plus total knee arthroplasty on the other side), with description of subsequent results at 36-months follow-up.

Understanding the human knee and its relationship to total knee replacement

The knee is the intermediate joint of the lower limb and it allows the movement between the femur, tibia and patella. Under normal conditions there is a normal distribution of the load forces on these three articular components in both the static load and during ambulation. The understanding of anatomy and knee biomechanics is important for the gait analysis, the diagnosis of joint diseases and the design and development of prosthetic implants. In the last decades comprehension of knee physiology and kinematics has led to the introduction of a wide range of enhanced prosthetic implant designs for a variety of indications. There are a number of types of total knee arthroplasty implant designs, which are intended to offer the surgeon options for individual patients. The various choices imply that each specific problem has a corresponding implant that provides a reliable solution. However, until the current date, it has not been possible to produce a prosthetic design fully restoring the complex kinematics of the normal knee joint.

Does low-constraint mobile bearing knee prosthesis give satisfactory results for severe coronal deformities? A five to twelve year follow up study

PURPOSE

Severe varus and valgus knee deformities traditionally are replaced with constrained implants, with a number of disadvantages. We present our results in this challenging group using a low constraint deep-dish mobile bearing implant design.

METHODS

One hundred fifty-four patients (170 arthroplasties) who underwent primary TKA using a deep-dish, mobile bearing posterior-stabilized implant for severe varus (HKA < 170°) or valgus (HKA > 190°) deformity between 2004 and 2009 were evaluated at a mean of 6.6 years post-operatively (minimum of 5 years).

RESULTS

Alignment improved from a pre-operative mean (±SD) varus deformity of 167.4° (±2.6°) and a mean (±SD) valgus deformity of 194.1° (±4.0°) to an overall mean (±SD) post-operative mechanical alignment of 178.6° (±3.2°). Twenty-three patients had post-operative varus alignment, five patients had post-operative valgus alignment and 134 knees were in neutral alignment (within 3° spread). Clinical scores at final follow-up were excellent (IKS score 93.8 (±7.4) and function score 82.4 (±20.2)). Three patients were re-operated upon: one deep infection, one periprosthetic fracture and one revision at 144 months for aseptic loosening of the femoral component. No patient was revised for instability or implant failure. The survival rate at five years was 99.4% and at ten years 98.6%.

CONCLUSIONS

Satisfactory outcomes can be achieved in patients with substantial varus or valgus deformities using low constraint deep-dish mobile bearing implant, standard approach and appropriate soft tissue releases.

Current surgical strategies for total arthroplasty in valgus knee

The majority of orthopaedic surgeons even currently agree that primary total arthroplasty in valgus knees with a deformity of more than ten degrees may prove challenging. The unique sets of bone and soft tissue abnormalities that must be addressed at the time of the operation make accurate axis restoration, component orientation and joint stability attainment a difficult task. Understanding the specific pathologic anatomic changes associated with the valgus knee is a prerequisite so as to select the proper surgical method, to optimize component position and restore soft-tissue balance. The purpose of this article is to review the valgus knee anatomical variations, to assess the best pre-operative planning and to evaluate how to choose the grade of constraint of the implant. It will also be underlying the up-to-date main approaches and surgical techniques be proposed in the English literature both for bone cuts and soft tissue management of valgus knees.

Long-term outcomes of primary constrained condylar knee arthroplasty

BACKGROUND

Although constrained condylar knee (CCK) inserts are widely used for total knee arthroplasty (TKA), their long-term outcomes remain unclear. We sought to evaluate patients with at least 10 years' follow-up after CCK TKA to identify potential adverse events (osteolysis, loosening, constraint-mechanism failure), assess functional outcomes with special emphasis on range of motion, and determine prosthesis survival.

HYPOTHESIS

Increasing constraint by implantation of a CCK insert does not increase the long-term frequencies of osteolysis or mechanical loosening.

MATERIAL AND METHODS

We studied 43 knees after Legacy(®) CCK TKA. The indication was severe deformity (n=20), pre-operative laxity (n=6), or failure to achieve intra-operative balancing (n=17). There were 41 patients with a mean age of 66 years (21-88). A history of one or more surgical procedures was noted for 27 (63%) knees. Outcome measures were the Hospital for Special Surgery (HSS) knee score, Knee Society Score (KSS), and change in the hip-knee-ankle (HKA) angle. Prosthesis survival was assessed using revision surgery for any reason or for reasons other than infection as the censoring criterion.

RESULTS

Complications other than venous thrombosis occurred in 16% of patients, including 3 who required revision surgery (septic loosening, n=2; and major instability in a patient with ipsilateral hip arthrodesis). No cases of osteolysis or aseptic loosening were recorded. Mean follow-up was 12.7 years (range, 10-14). At last follow-up, the HSS score had improved from 53 (26-83) pre-operatively to 80 (55-93), the KSS knee component from 42 (16-77) to 90 (77-99), and the KSS function component from 31 (0-80) to 61 (10-90) (P<0.001). Mean range of flexion increased from 109° (50°-140°) to 112° (90°-130°) (P=0.12). The HKA angle changed from 182°±15.5° (150°-210°) to 179.5°±2.5° (174°-184°) (P=0.5). The 11-year prosthesis survival rate was 88.5% (95% confidence interval, 0.69-0.94) overall and 97.7% (0.76-0.99) after excluding the cases of infection.

DISCUSSION

Long-term functional gains after CCK TKA were similar to those reported after standard posterior-stabilised TKA, with no cases of constraint-mechanism failure or osteolysis. The complication rate was higher, with decreased survival compared to standard TKA, but the knee deformities and/or instability were particularly severe and two-thirds of knees had a history of one or more surgical procedures.

Arthroplasty in the Valgus Knee: Comparison and Discussion of Lateral vs Medial Parapatellar Approaches and Implant Selection

Constrained implants are frequently used for primary total knee arthroplasty (TKA) in patients with moderate and severe genu-valgum (>10˚). This deformity presents corrective challenges for ligament release. The lateral-parapatellar approach has been advocated as an alternative to the traditional medial-parapatellar approach. Claimed advantages include better access for release of tight ligamentous structures, without requirement for release of the medial-collateral ligament. We present our comparative experience of the use of an unconstrained knee-replacement prosthesis inserted by the lateral-parapatellar approach in comparison to a constrained-knee prosthesis inserted via the medial-parapatellar approach. 49 primary total knee-replacements in 48 (6 males, 42 females) patients were performed; 32 through a lateral-parapatellar approach (group L) using an unconstrained-prosthesis and 17 through a medial-parapatellar approach more often requiring a constrained-prosthesis (group M). Mean preoperative valgus angle was 18.5 (range 11-34˚). Patient demographics (p=0.7) and valgus correctability were similar between the two groups. There was no significant difference in the mean post-operative valgus angle. This was 4.2˚ (range 1-9.5˚) using the lateral-parapatellar approach and 5.3˚ (range 0.3-10˚), p=0.12, using the medial-parapatellar approach. Transient common peroneal injury occurred in 2 patients, both group L, in the presence of valgus angles of greater than 20˚. To date no joints have been revised, or are unstable. The use of a lateral-parapatellar approach, appropriate soft tissue release, and an unconstrained PCL-preserving implant, yielded in all cases a stable, well aligned knee arthroplasty. This represents a viable alternative to the constrained-prosthesis using a medial-parapatellar approach in patients with moderate and severe genu-valgum.

The minimally invasive far medial subvastus approach for total knee arthroplasty in valgus knees

PURPOSE

The lateral approach in the valgus knee asks for a lot of soft tissue releases during the arthrotomy. The hypothesis of this study was that the far medial subvastus approach could be used in valgus knees and would guarantee both functional and radiological good to excellent results.

METHODS

This is a retrospective study on 78 patients (84 knees) undergoing primary total knee arthroplasty (TKA) for type I or II fixed valgus knees. The mean (SD) preoperative mechanical alignment was 187° (4°) HKA angle. Functional recovery, pain, tourniquet times, necessary soft tissue releases as well as radiological alignment were measured.

RESULTS

The Knee Score improved significantly from 45 (10) to 90 (10) (P < 0.05) and the function score improved as well from 35 (20) to 85 (10) (P < 0.05). Flexion improved from 110° (10°) to 137° (8°). Hospital stay was 4 (1.2) days. Alignment was corrected to 181° (1.5°) HKA angle with a postoperative joint line shift of +2.8 (3.2) mm. No clinical instability, as evaluated by the senior author, or osteolytic lines was observed at minimal one-year radiological follow-up.

CONCLUSION

The far medial subvastus approach is an excellent approach to perform Krackow type I and II TKA with primary PS implants.

Plateau-patella angle in evaluation of patellar height in osteoarthritis

BACKGROUND

The plateau-patella angle (PPA), recently introduced as a new and simpler method of measuring patellar height from the lateral radiograph, has the advantage of simplicity over previously described methods as it involves a single angular measurement without the need for calculations. The purpose of this study was to validate the use of the PPA as a measurement for patellar height in knees with moderate to severe osteoarthritis.

METHODS

A total of 331 patients who underwent total knee arthroplasty at our institution with radiographs prior to surgery were evaluated. Of those, 297 (89.2%) were felt to be adequate for review. Three observers with different levels of orthopedic training measured PPA, Insall-Salvati, Caton-Deschamps, and Blackburne-Peel indices on a subset of 50 consecutive patients. Interobserver agreement for each of the four measurements was calculated and correlation between each of the measurements within each observer was calculated. The measurement of the PPA was repeated. Intraobserver agreement for the PPA was determined and a normal range and distribution was defined for this population.

RESULTS

For the three observers, the mean PPA for the entire cohort was 25.55, 25.31, and 24.42. The intraclass correlation coefficient (ICC) was 0.81, The ICC and intraobserver assessment were the highest for the PPA compared with the other ratios. The PPA was found to correlate most strongly with the Blackburne-Peel method.

CONCLUSIONS

The plateau-patella angle is a reliable way to evaluate patellar height in the osteoarthritic population. The measurement demonstrated a higher interobserver reliability compared with previously described methods.

LEVEL OF EVIDENCE

Retrospective Level IV.

Clinical biomechanics of instability related to total knee arthroplasty

BACKGROUND

Tibiofemoral instability is a common reason for total knee arthroplasty failure, and may be attributed to soft tissue deficiency and incorrect ligament balancing. There are many different designs of implant with varying levels of constraint to overcome this instability; however there is little advice for surgeons to assess which is suitable for a specific patient, and soft tissue balance testing during arthroplasty is very subjective.

METHOD

The current theories on primary and secondary soft tissue restraints to anterior/posterior, varus/valgus, and internal/external rotational motion of the knee are discussed. The paper reviews biomechanics literature to evaluate instability in the intact and implanted knee.

FINDINGS

The paper highlights important intra- and extra-capsular structures in the knee and describes the techniques used by clinicians to assess instability perioperatively. In vitro cadaveric studies were found to be a very useful tool in comparing different implants and contributions of different soft tissues.

INTERPRETATION

In vitro cadaveric studies can be utilised in helping less experienced surgeons with soft tissue releases and determining the correct implant. For this to happen, more biomechanical studies must be done to show the impact of release sequences on implanted cadavers, as well as determining if increasingly constrained implants restore the stability of the knee to pre-deficient conditions.

Joint line changes and outcomes in constrained versus unconstrained total knee arthroplasty for the type II valgus knee

PURPOSE

The objective of this study was to compare the outcome of constrained and unconstrained primary total knee arthroplasty (TKA) in the management of the valgus deformity.

METHODS

This is a retrospective review of patients with type II valgus knee who underwent primary TKA from 1999 to 2011. There were fifty patients in Group 1 who underwent varus-valgus constrained TKA. They were matched with another fifty patients in Group 2 who underwent unconstrained TKA.

RESULTS

The mean joint line shift was significantly higher in Group 1 (+8 mm, SD 6 mm) than in Group 2 (+2 mm, SD 3 mm) (p = 0.03). At 2 years, there was no difference in anterior-posterior stability and mediolateral stability according to the Knee Society Score, and patients in Group 2 reported significantly better mean function score of 66.2 (SD 9.3) (mean 48, SD 7.1 in Group 1) (p = 0.002). Two patients (6 %) in Group 1 underwent revision surgery--one for a broken central peg and the other for aseptic loosening. Three patients (2 %) in Group 2 underwent revision surgery--two for global instability and one for poly wear. The estimated survivorship time was 8.3 years for constrained TKA and 12.0 for unconstrained TKA.

CONCLUSION

Constrained TKA was associated with more significant joint line changes for the management of valgus arthritic knee, when compared with unconstrained TKA.

LEVEL OF EVIDENCE

Retrospective study, Level III.

A new navigation-based technique for lateral distalizing condylar osteotomy in patients undergoing total knee arthroplasty with fixed valgus deformity

PURPOSE

In a prospective, consecutive study, a navigation-based technique for calculating the sliding distance of the lateral epicondyle prior to osteotomy in TKA surgery of fixed valgus deformity has been developed, and early results have been evaluated.

MATERIALS AND METHODS

Twenty-seven knees with a fixed valgus deformity undergoing TKA received this new treatment. Clinical scores and radiograph evaluation were performed preoperatively and 1-year postoperatively. Static and dynamic kinematic data were obtained from navigation at the beginning and at the end of surgery.

RESULTS

The calculated amount of sliding distance varied between 5 and 16 mm. No complications regarding this technique occurred. All clinical scores showed a significant improvement, and radiological evaluation showed a correction of all parameters in 100 % of patients.

CONCLUSION

With this navigation-based technique, it is possible to calculate the amount of sliding distance prior to osteotomy and obtain excellent early results. All axes have been corrected completely, and flexion and extension gaps were balanced. No specific complications of this technique have occurred so far.

LEVEL OF EVIDENCE

II.

Constraint choice in revision knee arthroplasty

PURPOSE

Along with the increase in primary total knee arthroplasty, there has been an increase in the number of revisions. The aim of this study was to propose a selection algorithm for the knee revision constraint according to the state of ligaments and to the bone defects Anderson Orthopaedic Research Institute Classification [AORI] classification. The hypothesis was that this algorithm would facilitate the appropriate choice of prosthesis constraint, thus providing stable components and a good long-term survivorship of the knee revisions.

METHODS

Sixty consecutive revision knee arthroplasties in 57 patients were prospectively evaluated. Prostheses implanted at revision included postero-stabilised, condylar constrained and rotating hinged, relative to the state of the ligaments and of the bone loss around the knee. The median follow-up was nine years (range, 4-12).

RESULTS

The median IKS knee and function scores and HSS score were 41 (15-62), 21.5 (12-43) and 34 (23-65) points, respectively, before the operation, and 81 (48-97), 79 (56-92) and 83.5 (62-98) points (p < 0.001) at the latest follow-up evaluation. The median ROM increased from 74° (29-110°) preoperatively to 121° (98-132°) (p < 0.01) at the final follow-up. Re-revision was necessary in five (8.3%) patients.

CONCLUSIONS

A selection algorithm for the revision implant constraint based on the state of ligaments and the bone loss AORI classification could provide stable knee reconstructions and long-term success of knee revisions.

Poor results of the Optetrak™ cemented posterior stabilized knee prosthesis after a mean 25-month follow-up: analysis of 110 prostheses

INTRODUCTION

The introduction of a new knee arthroplasty model, even if it differs from a validated implant by only a few details, should be followed by rigorous assessment. The Optetrak™ cemented posterior stabilized knee prosthesis evolved from the Insall prosthesis with a smaller tibial keel associated with a higher tibial cam and increased femorotibial congruency as well as a more posterior-stabilized trochlea.

HYPOTHESIS

We hypothesized that this implant with only minor modifications to the Insall prosthesis would provide as favorable results as the Insall prosthesis.

MATERIALS AND METHODS

A continuous series of 110 prostheses (106 patients) implanted between 2005 and 2007 was retrospectively analyzed with a mean follow-up of 25 months (range, 12-42 months) by an independent observer. The follow-up was based on the IKS score and the radiological assessment was conducted by three senior surgeons.

RESULTS

The mean IKS score was 83.7 (range, 13-100) points at the last follow-up, the mean function score was 82.6 (range, 30-100 points), and mean flexion was 120° (range, 80-140°). Seventeen patients (15%) were disappointed or dissatisfied, 25 knees (22%) were painful, requiring regular painkillers. The prostheses had a satisfactory mechanical axis, with a mean HKA angle of 177.4 ± 4°, but 25 prostheses (22%) presented rims evolving toward tibial implant loosening, and 24 (21%) developed signs of patellofemoral conflict. With follow-up less than 5 years, nine cases were revised for tibial loosening, three for patellofemoral instability, and one for patellofemoral pain. The cases of tibial loosening were particular because they occurred at the cement-tibial-implant interface. The cumulated survival rate at 36 months was 80.97 ± 9.1% and 76.74 ± 12% at 45 months.

DISCUSSION

This tibial implant with a small keel does not resist the stresses applied by posterior stabilization, with notably a higher level of stress than the Insall prosthesis from which it was derived. In cases of centering defect, the design of the trochlea can lead to impingement between the edges of the patella and the prominent edges of the prosthetic trochlea. We have suspended implantation of this prosthesis and continue to monitor the progression of patients having received these implants.

LEVEL OF EVIDENCE

Level IV, retrospective study.

Total knee arthroplasty in severe valgus knee deformity: comparison of a standard medial parapatellar approach combined with tibial tubercle osteotomy

PURPOSE

Primary TKA in valgus knees with a deformity of more than ten degrees may prove challenging, since bone and soft tissue abnormalities make accurate axis restoration, component orientation and joint stability attainment a difficult task. The purpose of this study was to determine which approach is optimal in these patients, by comparing the standard medial parapatellar approach to a lateral parapatellar combined with a tibial tubercle osteotomy (TTO).

METHODS

Forty-four valgus knees--with an axis deviation ranging from 15 to 36 degrees (mean 24°)--were dealt with primary TKA and followed up for a minimum period of 7 years. Lateral parapatellar arthrotomy combined with TTO was performed in 22 individuals (Group A) and a standard medial parapatellar capsulotomy in the remaining patients (Group B). The International Knee Society System Score (IKSS) was used for clinical evaluation. Radiological assessment was performed yearly postoperatively using long films for assessment of the anatomical axis.

RESULTS

The postoperative IKSS scores showed no significant statistical difference between groups A and B (P < 0.05). In the alignment parameter, however, residual valgus deviation occurred in 9% of patients from Group A and in 32% from Group B. No late-onset instability was displayed.

CONCLUSION

Lateral parapatellar approach combined with TTO may prove highly beneficial in significant valgus deformities, as the anatomical axis is restored accurately and soft tissue release of the lateral contracted structures facilitated to an important extent.

RADIOGRAPHIC ASSESSMENT OF THE OPENING WEDGE PROXIMAL TIBIAL OSTEOTOMY

Objective: To radiographically evaluate individuals who underwent opening wedge proximal tibial osteotomy, with the aim of analyzing the proximal tibial slope in the frontal and sagittal planes, and the patellar height. Method: The study included 22 individuals who were operated at the National Traumatology and Orthopedics Institute (INTO) for correction of varus angular tibial deviation using the opening wedge osteotomy (OWO) technique with the Orthofix monolateral external fixator. Patients with OWO whose treatment was completed between January 2000 and December 2006 were analyzed. The measurement technique consisted of using anteroposterior radiographs with loading and lateral views with the operated knees flexed at 30°. Results: There were no statistically significant differences between the pre and postoperative tibial slope and patellar height values in the patients evaluated. Conclusion: Opening wedge proximal tibial osteotomy is a technique that avoids the problems presented by high proximal tibial osteotomy, since it is done without causing changes to the extensor mechanism, ligament imbalance or distortions in the proximal tibia.