Preoperative Varus Deformity Research Articles

Posterior Cruciate-Retaining Total Knee Arthroplasty

Total knee arthroplasty has evolved into a very successful procedure to relieve pain and restore function in the arthritic knee with advanced structural damage. Optimal results are dependent on the restoration of alignment and ligament stability. Operative techniques involve either preservation of the posterior cruciate ligament or substitution of its function through increased prosthetic constraint. The vast majority of knees do not require cruciate substitution to establish appropriate stability and function. This video outlines the operative technique used by the author for posterior cruciate retaining total knee arthroplasty in a patient with a pre-operative varus deformity.

Postoperative alignment of TKA in patients with severe preoperative varus or valgus deformity: is there a difference between surgical techniques?

BackgroundThere have been conflicting studies published regarding the ability of various total knee arthroplasty (TKA) techniques to correct preoperative deformity. The purpose of this study was to compare the postoperative radiographic alignment in patients with severe preoperative coronal deformity (≥10° varus/valgus) who underwent three different TKA techniques; manual instrumentation (MAN), computer navigated instrumentation (NAV) and patient specific instrumentation (PSI).MethodsPatients, who received a TKA with a preoperative coronal deformity of ≥10° with available radiographs were included in this retrospective study. The groups were: MAN; n = 54, NAV; n = 52 and PSI; n = 53. The mechanical axis (varus / valgus) and the posterior tibial slope were measured and analysed using standing long leg- and lateral radiographs.ResultsThe overall mean postoperative varus / valgus deformity was 2.8° (range, 0 to 9.9; SD 2.3) and 2.5° (range, 0 to 14.7; SD 2.3), respectively. The overall outliers (>3°) represented 30.2% (48 /159) of cases and were distributed as followed: MAN group: 31.5%, NAV group: 34.6%, PSI group: 24.4%. No significant statistical differences were found between these groups. The distribution of the severe outliers (>5°) was 14.8% in the MAN group, 23% in the NAV group and 5.6% in the PSI group. The PSI group had significantly (p = 0.0108) fewer severe outliers compared to the NAV group while all other pairs were not statistically significant.ConclusionsIn severe varus / valgus deformity the three surgical techniques demonstrated similar postoperative radiographic alignment. However, in reducing severe outliers (> 5°) and in achieving the planned posterior tibial slope the PSI technique for TKA may be superior to computer navigation and the conventional technique. Further prospective studies are needed to determine which technique is the best regarding reducing outliers in patients with severe preoperative coronal deformity.

Medial Tibial Reduction Osteotomy is Associated with Excellent Outcomes and Improved Coronal Alignment

Background: The medial tibial reduction osteotomy (MTRO) was introduced to achieve coronal ligamentous balance in total knee arthroplasty (TKA) patients with substantial preoperative varus deformity. Limited data exists on the outcomes of patients requiring an MTRO. This study compares outcomes of a matched cohort of patients that either required or did not require an MTRO during TKA.Methods: A retrospective review was performed on 67 patients that underwent an MTRO during primary TKA to achieve coronal balance. This patient population was matched 1:1 to another cohort of TKA patients by age, gender, and BMI that did not require an MTRO. A clinical and radiographic evaluation was utilized to compare the two cohorts.Results: Preoperatively, the tibiofemoral angle was 3.42° valgus versus 6.12° varus in the control and MTRO cohorts respectively (p=0.01). Mean postoperative tibiofemoral angles were 3.40° versus 2.43° valgus respectively. Postoperative Knee Society Scores were superior in the MTRO cohort (183.84 versus 174.58; p=0.04). Intraoperatively, no superficial MCL releases were required to achieve coronal balance in either cohort. Complications were similar and limited in both groups. Medial tibial bone resorption was observed in 64% of MTRO subjects averaging 2.02mm versus only 0.3mm in the control cohort ( p=0.01).Conclusion: Patients requiring an MTRO achieved similar alignment and superior knee scores compared to a control cohort with less varus deformity. This procedure eliminated the need for release of the superficial MCL. Resorption of medial tibial bone was commonly observed, possibly secondary to saw-induced thermal necrosis associated with performing an MTRO.

No impact of under-correction and joint line obliquity on clinical outcomes of total knee arthroplasty for the varus knee.

It has been hypothesized that under-correction of a preoperative varus deformity may be more natural and improve outcomes after total knee arthroplasty (TKA). This study's purpose was to assess the impact of hip-knee-ankle (HKA) alignment and joint line obliquity on TKA outcomes for the varus knee. All patients with a preoperative varus deformity received both preoperative and postoperative standing, full-length radiographs from which two independent observers performed radiographic measurements including the HKA axis and mechanical medial proximal tibial angle (mMPTA). Patients were categorized based on their HKA into neutral (0° ± 3°), mild varus (-6° to -3°), severe varus (≤ -6°), and valgus (>3°) cohorts, and separately categorized based on their mMPTA into neutral (90° ± 2°), mild varus (86°-88°), severe varus (<86°), and valgus (>92°) cohorts. Two hundred and fifty-six patients (mean age 63.8 ± 9.0 years, BMI 33.0 ± 6.2kg/m2, follow-up 1.3 ± 0.6 years) were included. There was no difference in the postoperative SF-12 physical component, mental component, Oxford knee, Forgotten Joint Score, or incremental improvement in scores based on the postoperative alignment category for either the HKA or mMPTA. There was no correlation between the magnitude of change in HKA (r = 0.03-0.1) and mMPTA (r = 0.02-0.1) from preoperatively to postoperatively with clinical outcomes. In patients undergoing TKA for a preoperative varus deformity, a specific postoperative HKA or mMPTA alignment category was not associated with improved outcomes. Therefore, categorization of optimal postoperative alignment after TKA may not be possible as static, coronal alignment is just one of many variables that can impact clinical outcomes. Future investigations focusing on the combination of static images with dynamic examinations and ligamentous balancing may shed further insight into the controversy and importance of coronal alignment following TKA. III.

Algorithmic pie-crusting of the medial collateral ligament guided by sensing technology affects the use of constrained inserts during total knee arthroplasty.

Intra-operative sensing technology is an alternative to standard techniques in total knee arthroplasty (TKA) for determining balance by providing quantitative analysis of loads and point of contact throughout a range of motion. We used intra-operative sensing (VERASENSE-OrthoSensor, Inc.) to examine pie-crusting release of the medial collateral ligament in knees with varus deformity (study group) in comparison to a control group where balance was obtained using a classic release technique and assessed using laminar spreaders, spacer blocks, manual stress, and a ruler. The surgery was performed by a single surgeon utilizing measured resection and posterior-stabilized, cemented implants. Seventy-five study TKAs were matched 1:3 with 225 control TKAs. Outcome variables included the use of a constrained insert, functional- and knee-specific Knee Society score (KSS) at six weeks, fourmonths, and one year post-operatively. Outcomes were analyzed in a multivariate model controlling for age, sex, BMI, and severity of deformity. The use of a constrained insert was significantly lower in the study group (5.3 vs. 13.8%; p = 0.049). The use of increased constraint was not significant between groups with increasing deformity. There was no difference in functional KSS and knee-specific KSS between groups at any follow-up interval. An algorithmic pie-crusting technique guided by intra-operative sensing is associated with decreased use of constrained inserts in TKA patients with a pre-operative varus deformity. This may cause a positive shift in value and cost savings.

Comparing the accuracy of high tibial osteotomies between computer navigation and conventional methods

Background: The accuracy of correction has been shown to be an important determinant in long-term outcomes of patients who were treated with a medial open-wedge high tibial osteotomy (HTO) who suffer from unicompartmental osteoarthritis (OA). Computer navigation systems have the potential to improve surgical precision. The purpose of this study was to compare radiographic outcomes between patients treated with a navigation system and those treated through conventional methods of assessing alignment intra-operatively. The null hypothesis was that the method of assessing the alignment intra-operatively would make no difference in the accuracy of correction.Methods: In this retrospective study, 107 patients with medial varus OA who were managed by open-wedge HTO were included. Of the 107 patients, 41 were treated using an intraoperative navigation system and 66 were treated using conventional methods. Pre-operative and post-operative single-leg, long-leg standing alignment films were used to determine the extent of pre-operative varus deformity and the post-surgical correction achieved compared to the predetermined target range.Results: The navigational system had eight instances of software malfunction (19.5%) intra-operatively and correction was determined using the cable method. These results were analyzed as part of the conventional group. Post-operative radiographic differences were significant between the two groups. In the navigation group, 75.8% of the patients were corrected within the target range compared to 66.2% in the conventional group. More patients were also under corrected (to the point of remaining in varus) using conventional methods compared to a navigation system. There was no statistically significant difference in the degree of correction in the sagittal plane between the two groups. Regardless of the method used for checking alignment intra-operatively, there was a statistically significant difference in post-operative weight-bearing measurements when the surgeon had intra-operative axial loading versus when they did not.Conclusion: For coronal plane corrections, the navigation system was shown to have greater success in achieving the desired correction value and in having fewer patients who were under corrected. Despite the measurement technique a surgeon chooses to assess the accuracy of correction, axial loading the extremity in order to simulate the weight-bearing film alignment post-operatively is important to maximize the accuracy of correction needed.

Treatment of post-traumatic elbow deformities in children with the Ilizarov distraction osteogenesis technique

ObjectiveThe present study assessed functional and radiographic outcomes of distraction osteogenesis treatment of post-traumatic elbow deformities in children. MethodsEight children were treated between 2008 and 2013 for post-traumatic elbow deformities using distraction osteogenesis. Mean age at time of operation was 10.9 years. Six patients had varus and 2 had valgus deformity. Magnitude of correction, fixator index, complications, carrying angle, and elbow range of motion were assessed. Functional results were graded according to protocol of Bellemore et al. ResultsMean follow-up was 43 months. Mean preoperative varus deformity in 6 patients was 29.2° and valgus deformity in 2 patients was 28.5°. Preoperative flexion and extension of elbow were 123.8° and −10.6°, respectively. Mean carrying angle was 9° valgus at last follow-up. Mean flexion and extension were 134.4° and −6.0°, respectively. Change in carrying angle was statistically significant (p = 0.002). There were 2 grade 1 pin tract infections and 1 diaphyseal fracture of humerus. Functional outcome was rated excellent in 7 patients and good in 1 patient. ConclusionIlizarov distraction osteogenesis is a valuable alternative in treatment of elbow deformities in children. The surgical technique is simple and correction is adjustable. Gradual correction prevents possible neurovascular complications and minimally invasive surgery produces less scarring. Compliance of patient and family is key factor in the success of the outcome. Level of evidenceLevel IV, therapeutic study

Medial Tibial Stress Shielding: A Limitation of Cobalt Chromium Tibial Baseplates

BackgroundStress shielding is a well-recognized complication associated with total knee arthroplasty. However, this phenomenon has not been thoroughly described. Specifically, no study to our knowledge has evaluated the radiographic impact of utilizing various tibial component compositions on tibial stress shielding. MethodsWe retrospectively reviewed 3 cohorts of 50 patients that had a preoperative varus deformity and were implanted with a titanium, cobalt chromium (CoCr), or an all polyethylene tibial implant. A radiographic comparative analysis was performed to evaluate the amount of medial tibial bone loss in each cohort. In addition, a clinical outcomes analysis was performed on the 3 cohorts. ResultsThe CoCr was noted to have a statistically significant increase in medial tibial bone loss compared with the other 2 cohorts. The all polyethylene cohort had a statistically significantly higher final Knee Society Score and was associated with the least amount of stress shielding. ConclusionThe CoCr tray is the most rigid of 3 implants that were compared in this study. Interestingly, this cohort had the highest amount of medial tibial bone loss. In addition, 1 patient in the CoCr cohort had medial soft tissue irritation which was attributed to a prominent medial tibial tray which required revision surgery to mitigate the symptoms.

Computer-assisted surgery does not improve the rotational alignment of the femoral component in total knee arthroplasty for severe genu varus deformity

Background: Accurate femoral rotational alignment is critical for successful total knee arthroplasty (TKA). Debates exist about whether computer-assisted surgery-TKA (CAS-TKA) improves the accuracy of femoral rotational alignment. We hypothesize that it is related to the severity of the preoperative genu varus deformity and that CAS-TKA is beneficial under certain circumstances. Methods: Patients who had osteoarthritis with genu varus deformity and underwent conventional TKA or CAS-TKA between January 2007 and July 2013 at our hospital were enrolled. Based on the degree of preoperative deviation from the mechanical axis (MA), the patients were divided into three subgroups at 5-degree intervals: (1) varus deformity of ＜ 10 degrees, (2) 10–14.9 degrees, and (3) ≥ 15 degrees. Computed tomography was used to determine whether CAS-TKA provided better femoral rotational alignment than did conventional TKA. Component and limb alignment were also radiographically compared. Results: One hundred seventy-three knees on 128 patients met the inclusion criteria. For patients in the ＜ 10 degrees and 10–14.9 degrees groups, the component alignments and postoperative mechanical axes were not significantly different between conventional and CSA-TKA. For patients in the ≥ 15 degrees group, however, the femoral flexion angle was significantly (p ＜ 0.001) better for CSA-TKA, but not for the femoral valgus, tibial valgus, tibial flexion, or femoral rotational angles. Conclusions: CAS-TKA does not improve the accuracy of rotational alignment of the femoral component in patients with genu varus deformity. Level of Evidence: Therapeutic Level III.

Computer assisted alignment of opening wedge high tibial osteotomy provides limited improvement of radiographic outcomes compared to flouroscopic alignment

IntroductionThere are numerous methods available to assist surgeons in the accurate correction of varus alignment during medial opening wedge high tibial osteotomy (MOWHTO). Preoperative planning performed with radiographs or more recently intraoperative computer navigation software has been used. The aim of the study was to compare the accuracy of computer navigated versus non-navigated techniques to correct varus alignment of the knee. MethodThe preoperative and postoperative radiographs of 117 knees that underwent MOWHTO were investigated to assess radiographic limb alignment 12-months postoperatively. The desired correction was defined as a weight bearing line (Mikulicz point {MP}) 58% of the width of the tibial plateau from the medial tibial margin. Sixty-five knees were corrected using a conventional technique and 52 knees were corrected using computer navigation. ResultsThe mean MP percentage was 59% in the navigated group, compared with 56% in the fluoroscopic group (p=0.183). 51.9% of the navigation knees were corrected to within five percent of the desired correction, in contrast to 38.5% of the fluoroscopically corrected knees (p=0.15). 71.2% of the navigated knees were corrected to within 10% of the desired correction, compared with 63.1% of the fluoroscopically corrected knees (p=0.36). Large preoperative deformities were more accurately corrected with navigation assistance (57% vs 49%, p=0.049). ConclusionNo statistically significant difference was found in the radiographic correction of varus alignment twelve months postoperatively between navigated and fluoroscopic techniques of MOWHTO. However, a subgroup analysis demonstrated that larger preoperative varus deformities may be more accurately corrected using computer navigation.

Medial cortical fractures in computer-assisted closing-wedge high tibial osteotomy

BackgroundWe evaluated the incidence of medial cortical fracture and influence on the loss of the correction angle in computer-assisted closing-wedge high tibial osteotomy. MethodsUsing a navigation system, 200 closing-wedge high tibial osteotomies were performed. The correction angle was defined as the difference between the pre- and postoperative medial proximal tibial angles. The change in the medial proximal tibial angle was calculated as the difference between the medial proximal tibial angles two weeks and one year postoperatively. The medial cortical fractures of the osteotomy site were evaluated. Their incidence, risk factors, and influence on the loss of correction angle were analyzed. ResultsThe incidence of non-displaced cortical breakage and displaced cortical fracture was 28.0% and 6.5%, respectively. Medial cortical fracture was more frequent in younger patients and patients with severe preoperative varus deformity. The average correction angle was significantly larger in the displaced cortical fracture group (9.6° vs. 12.7°, p<0.001). The average change in the medial proximal tibial angle in the no fracture, non-displaced cortical breakage, and displaced cortical fracture groups was 0.7°, 1.8°, and 4.4°, respectively (p<0.001). ConclusionsMedial cortical fracture could not be prevented in all knees, even using the navigation system. The risk of medial cortical fracture and loss of the correction angle was increased, particularly when a greater correction angle is required in young patients. Level of evidenceIV

Outcomes of Ankle Arthroplasty with Preoperative Varus Deformity of More Than 20 Degrees: Comparison with the Group of Varus Deformity of Less Than 20 Degrees

Outcomes of Ankle Arthroplasty with Preoperative Varus Deformity of More Than 20 Degrees: Comparison with the Group of Varus Deformity of Less Than 20 Degrees

Correlation between Quadriceps Endurance and Adduction Moment in Medial Knee Osteoarthritis.

It is not clear whether the strength or endurance of thigh muscles (quadriceps and hamstring) is positively or negatively correlated with the adduction moment of osteoarthritic knees. This study therefore assessed the relationships between the strength and endurance of the quadriceps and hamstring muscles and adduction moment in osteoarthritic knees and evaluated predictors of the adduction moment. The study cohort comprised 35 patients with unilateral medial osteoarthritis and varus deformity who were candidates for open wedge osteotomy. The maximal torque (60°/sec) and total work (180°/sec) of the quadriceps and hamstring muscles and knee adduction moment were evaluated using an isokinetic testing device and gait analysis system. The total work of the quadriceps (r = 0.429, P = 0.037) and hamstring (r = 0.426, P = 0.045) muscles at 180°/sec each correlated with knee adduction moment. Preoperative varus deformity was positively correlated with adduction moment (r = 0.421, P = 0.041). Multiple linear regression analysis showed that quadriceps endurance at 180°/sec was the only factor independently associated with adduction moment (β = 0.790, P = 0.032). The adduction moment of osteoarthritic knees correlated with the endurance, but not the strength, of the quadriceps muscle. However, knee adduction moment did not correlate with the strength or endurance of the hamstring muscle.

Knee Function and Subjective Stability Following Total Condylar Arthroplasty in Joints with Preoperative Varus or Valgus Deformity.

Total knee arthroplasty in joints with valgus or varus deformity is technically demanding. Careful soft tissue balance as well as restitution of anatomical knee axis has a profound effect on postoperative function of the joint, however little is known about differences in subjective stability following surgery between preoperative valgus and varus knees. Studied group consisted of 60 patients who underwent total condylar knee arthroplasty with one type of implant (Stryker Triathlon). Mean follow-up was 2,9 years (1-6 years). The group included 25 patients with valgus and 35 patients with varus preoperative deformity. All patients filled Knee Injury and Osteoarthritis Outcome Score (KOOS) forms. Detailed clinical and radiological assessment was performed. Mean KOOS score was slightly higher in patients with varus deformity, as compared to cases with valgus deformity. At physical examination higher LCL deficiency rate was observed in varus knees. Subjective instability was reported by eight patients (5 valgus and 3 varus). In all cases instability coexisted with decreased MCL tightness and implant position was correct in those patients. No subjective instability was reported by patients with clinical LCL deficiency. Furthermore KOOS scores in these patients were higher (85,8) as compared to cases with decreased MCL tension (79,1). 1. In patients with proper implant alignment subjective instability is related to postoperative MCL deficiency, regardless preoperative deformity in coronal plane. 2. The post-op LCL laxity does not compromise subjective stability, nor influence subjective outcome, as demonstrated with KOOS scores.

Improved femoral component rotation in advanced genu valgum deformity using computer-assisted measured resection total knee arthroplasty.

BackgroundAccurate femoral rotational alignment is of vital importance for successful total knee arthroplasty (TKA). The value of computer-assisted surgery TKA (CAS-TKA) in increasing the accuracy of femoral rotational alignment remains controversial. We hypothesize that outcomes are related to the severity of preoperative varus and valgus deformity and that CAS-TKA may be beneficial under certain circumstances.MethodsBetween January 2007 and December 2013, patients with osteoarthritis and varus angulation in the mechanical axis (MA) ≥ 15° and valgus angulation in the MA ≥ 10° (based on hip-to-ankle standing radiography) who underwent TKA were divided into four groups. CAS-TKA and conventional TKA outcomes were compared in patients who had preoperative advanced genu varum and advanced genu valgum deformities. The accuracy of component alignment and postoperative limb alignment was determined using radiographic parameters and computed tomography (CT).ResultsOne hundred and eight patients (144 knees) were included in the analysis. For patients with preoperative advanced genu varum deformity, a significant difference was detected in the sagittal femoral angle (p < 0.001), but no significant improvement of femoral rotational alignment was noted (p = 0.127). In patients with preoperative advanced genu valgum deformity, a significant difference was found in the sagittal femoral angle (p = 0.034). The femoral rotational angle was significantly closer to the proper position in the CAS-TKA group (p < 0.001). When comparing the percentage of knees achieving the proper alignment, there was a decrease in the amount of outlier for the femoral rotational angle for CAS-TKA in advanced genu valgum deformity (p = 0.011).ConclusionsOur data demonstrate that CAS-TKA is beneficial in obtaining proper femoral rotational alignment in patients with advanced genu valgum deformity (preoperative MA ≥ 10° valgus). In patients with advanced genu varum deformity (preoperative MA ≥ 15° varus), CAS-TKA did not improve the femoral rotational alignment.

Total ankle replacement for posttraumatic arthritis

Background and purpose — Most studies on total ankle replacement (TAR) have used a case mix of patients. We evaluated the outcome of TAR performed for end-stage arthritis either because of fracture or ligamentous injury.Patients and methods — We prospectively followed 88 consecutive patients (50 postfracture ankles and 40 ankles with instability arthritis (2 bilateral)) who underwent TAR between 2001 and 2009. Mean follow-up for both groups was 5 years.Results — Preoperative varus deformity of 10° or more was present in 23 ankles in the instability group. At 6 years, survival with revision or salvage fusion as an endpoint was 87% (95% CI: 74–99) in the postfracture group and 79% (95% CI: 63–94) in the instability group. Progressive periprosthetic osteolysis was seen in 23 ankles, and required salvage fusion in 6. The number of reoperations was similar in both groups. Clinical outcome, as assessed with 2 ankle scores and 2 questionnaires, showed good results and was similar at the latest follow-up.Interpretation — The outcome was similar in the postfracture and instability groups and also similar to that reported in series including a case mix of patients. In contrast to earlier reports, preoperative frontal plane deformity in this series was not identified as a risk factor for failure.

A Unique Pattern of Peri-Prosthetic Fracture Following Total Knee Arthroplasty: The Insufficiency Fracture

An isolated periprosthetic compression fracture following total knee arthroplasty has not been described in periprosthetic fracture classifications. Thus, the purpose is to describe this unique type of fracture based on clinical and radiographic analysis and identify the incidence and potential risk factors of this fracture. A retrospective chart review was performed from a database of 5864 primary total knee. A total of 56 (0.9%) periprosthetic fractures were identified with 15 (26.8%) of them demonstrating an isolated lateral compression fracture. Patients exhibiting this fracture pattern had a mean preoperative varus deformity of 176.3° and had poor bone quality (T score: −2.1). It is important to recognize that a compression fracture is not an infrequent finding and that further workup maybe warranted when clinical suspicion is high.

Clinical faceoff: Neutrally versus kinematically aligned TKA.

While the number of primary TKAs completed in the United States is expected to increase dramatically in the years to come, approximately 20% of patients undergoing primary TKA are dissatisfied with the procedure [5, 11]. As such, substantial healthcare resources have been devoted to the development and use of patient-specific instrumentation (PSI), computer navigation, robotics, and other tools that help achieve a neutrally aligned TKA in the coronal plane [1, 2, 14]. On the other hand, some investigators support a different approach: The concept of a kinematically aligned TKA [6, 8–10]. In general terms, a neutrally aligned TKA cuts the distal femur and proximal tibia 90° to the respective mechanical axes, while a kinematically aligned TKA incorporates 3° of varus into the tibia and an additional 3° of valgus into the femur. However, there remains considerable controversy in this area, in large measure because of a relative paucity of research comparing the approaches. As such, I have invited two internationally known experts to discuss these two approaches to obtaining a well-aligned TKA – the neutrally aligned and kinematically aligned techniques.

Comparison of Cruciate Retaining and PCL Sacrificing TKA with Respect to Medial and Lateral Gap Differences in Varus Knees After Medial Release

We aimed to clarify whether the increase in medial gap after medial release is influenced by the retention or sacrifice of posterior cruciate ligament (PCL) during navigation-assisted total knee arthroplasty. After matched pairs were done according to the equality of preoperative varus deformity and medial collateral laxity, 54 knees of each type were available for this study. In the PCL sacrificing group, the mediolateral gap difference significantly increased in both flexion and extension as the preoperative mechanical axis angle increased whereas in the cruciate retaining group, the mediolateral gap difference did not show this tendency. When preoperative mechanical axis angles were over 10.4° in extension and over 7.7° in flexion, the medial gap showed greater increases in PCL sacrificing groups than in cruciate retaining groups.

Different femorotibial contact on the weight-bearing: midflexion between normal and varus aligned knees after total knee arthroplasty

The influence of residual malalignment on biomechanical analysis after total knee arthroplasty (TKA) is currently uncertain. The hypothesis is that postoperative alignment would influence the in vivo kinematics after TKA, under weight-bearing conditions but not under non-weight-bearing condition. The purpose of the present study was to compare weight-bearing and non-weight-bearing conditions and to evaluate the effect of the postoperative alignment on the in vivo kinematics after posterior cruciate ligament-retaining TKA during midflexion using 2-dimensional/3-dimensional registration. Thirty knees of 30 patients with pre-operative varus deformity were divided into 2 groups according to their postoperative alignment: the normal alignment group (N = 21) and the varus alignment group (N = 9). Under weight-bearing conditions, the varus alignment group showed a significant posterior displacement of the medial femoral condyle (flexion: 80°, 90° P < 0.05) and a significant anterior displacement of the lateral femoral condyle (flexion: 10° P < 0.01, 20° P < 0.05, and extension: 10°, 20° P < 0.01, 30°, 40° P < 0.05) as compared with the normal alignment group. In contrast, no significant difference in the medial and lateral femoral condyle positions under non-weight-bearing conditions was observed between the normal and varus alignment groups. The postoperative alignment influenced knee kinematics under weight-bearing conditions. The weight load influenced knee kinematics through posterior tibial slope and induced greater lateral femoral condyle mobility, which might explain the better clinical and functional outcome. These findings contribute to gaining a proper understanding of the in vivo kinematics of the postoperative varus alignment and might be useful for orthopaedic surgeons in the achievement of patient satisfaction. III.