Computer assisted versus conventional total knee replacement: a comparison of tourniquet time, blood loss and length of stay

Aims and introductionThe aim of this study was to assess whether navigated total knee arthroplasty (TKA) reduces peri-operative blood loss and post-operative length of stay when compared to conventional total knee arthroplasty techniques.Patients and methodsA retrospective case-note review of 143 patients undergoing primary elective total knee arthroplasty was carried out. Two surgeons in this institution perform conventional knee arthroplasty using intramedullary alignment with another two surgeons using the computer assisted technique. Blood losses were calculated using the Meunier et al. (2008) [23] method for calculation of peri-operative blood loss. This is based on changes in peri-operative blood indices compared to the patient's theoretical total blood volume which is calculated using the patient's pre-operative height and weight. Tourniquet time and post-operative length of stay for the two techniques of arthroplasty were also recorded.ResultsSixty eight patients underwent conventional TKA and 75 patients had navigated TKA's performed. This data showed no significant difference in blood loss (p = 0.56) or post-operative length of stay (p = 0.36). A significant difference in tourniquet time between the two techniques was demonstrated (p = 0.01).ConclusionIn this study there was no significant reduction in post-operative length of stay and peri-operative blood loss when using computer-assisted techniques. There was an increase in tourniquet time with the computer-assisted technique that may have implications upon work productivity for primary cemented knee arthroplasty.     

Patient specific cutting guides versus an imageless,computer-assisted surgery system in total knee arthroplasty

BackgroundPatient specific cutting guides (PSC) in total knee arthroplasty (TKA) have recently been introduced, in which preoperative 3-dimensional imaging is used to manufacture disposable cutting blocks specific to a patient's anatomy. The purpose of this study was to compare the alignment accuracy of PSC to an imageless CAS system in TKA.MethodsThirty-seven patients (41 knees), received a TKA using an imageless CAS system. Subsequently, 38 patients (41 knees), received a TKA using a MRI-based, PSC system.Postoperatively, standing AP hip-to-ankle radiographs were obtained, from which the lower extremity mechanical axis, tibial component varus/valgus, and femoral component varus/valgus mechanical alignment were digitally measured. Each measurement was performed by two blinded, independent observers, and interclass correlations were calculated. A student's two-tailed t test was used to compare the two cohorts (p-value < 0.05 = significant).ResultsIn the PSC cohort, 70.7% of patients had an overall alignment within 3° of a neutral mechanical axis (vs. 92.7% with CAS, p = 0.02), 87.8% had a tibial component alignment within 2° of perpendicular to the tibial mechanical axis (vs. 100% with CAS, p = 0.04), and 90.2% had a femoral component alignment within 2° of perpendicular to the femoral mechanical axis (vs. 100% with CAS, p = 0.2). Interclass correlation coefficients were good to excellent for all radiographic measurements.ConclusionWhile PSC techniques appear sound in principle, this study did not demonstrate patient specific cutting guides to obtain the same degree of overall mechanical and tibial component alignment accuracy as a CAS technique.Level of evidenceIII: Retrospective cohort study.     

Pre-operative analysis of lower limb coronal alignment — A comparison of supine MRI versus standing full-length alignment radiographs

BackgroundIn this study we compare the results of pre-operative standing full-length alignment (SFLA) radiographs with supine MRI assessment of the lower limb alignment prior to MRI based patient specific total knee arthroplasty (TKA).MethodsImaging was performed in 45 knees (45 patients). Assessment of SFLA radiographs was performed by three independent assessors. Inter-observer correlation was high and so the mean values were calculated. This data was then compared to MRI alignment data used to create the patient specific cutting jigs.ResultsThe range of alignment on SFLA radiographs ranged from + 25° to − 13° versus + 20° to − 11° with MRI. The mean difference between techniques was 2° (range 0–8°, SD ± 3°). Supine MRI under-estimated the degree of deformity in 31/45 (69%) cases. In 25/45 (56%) cases the supine MRI result was within ± 2° of the value on SFLA radiographs, 31/45 (69%) were within ± 3° and 38/45 (84%) within ± 5°. There was no correlation between the degree of varus/valgus deformity and the magnitude of the difference between imaging modalities (Spearman's r² = 0.02, p = 0.41).ConclusionsThe findings from this study would indicate that supine MRI underestimates the degree of deformity at the knee joint, a conclusion which may be important for pre-operative planning or follow-up of corrective osteotomy or TKA.     

The effect of knee flexion during tourniquet inflation,fat pad excision and lateral tibial release on patellar subluxation during MIS TKA

We compared the distance of patellar subluxation (lateral patellar displacement) during MIS TKA arthrotomy among sequential variations of tourniquet application and soft tissue release in a consecutive series of 40 knees. The distance of patellar subluxation from the Whiteside's line was measured for every knee under four consecutive conditions; A) the tourniquet inflated with knee in full extension, B) no tourniquet pressure applied, C) the tourniquet inflated with knee in deep flexion, and D) the tourniquet inflated with knee in deep flexion and lateral tibial release (a limited subperiosteal soft tissue dissection including limited patellar fat pad excision and limited capsular release from the upper lateral tibial plateau). There were 28 women and 12 men with the average age of 70 years and the average BMI of 25.5. All knees had preoperative flexion more than 110°. The tourniquet pressure ranged from 280 to 300 mm Hg. The average skin incision length was 9 cm. The average measured distance of condition A, B, C and D were 10, 14.5, 15.8 and 22 mm, respectively with significant difference (p < 0.001). The distance of patellar subluxation correlated between conditions A) and C) (r², 0.67) and between conditions C) and D) (r², 0.72) in the studied group. However, there was no statistical difference of measured distance between group with condition B and C (p = 0.40). In conclusion, when MIS TKA is performed using the tourniquet, inflating the tourniquet with knee in deep flexion provided better arthrotomy exposure than the knee in full extension. Combined inflating tourniquet in deep knee flexion and lateral tibial release provided the greatest arthrotomy visualization.     

The tibial crest as a practical useful landmark in total knee arthroplasty

BackgroundThe middle one-third of the tibial crest in the coronal plane and the fibula in the sagittal plane are known as landmarks for extramedullary guides in total knee arthroplasty (TKA). However, there are few foundational anatomic studies about them. We conducted this study to confirm whether these landmarks are reliable.MethodsWe evaluated 100 Japanese knees using 3D imaging software. We examined our data for correlations between the angle of deviation from the mechanical axis and patient-specific factors (i.e. hip-knee-ankle angle, tibial length, tibial bowing, and tibial torsion) to determine whether there are any individual factors affecting their reliability.ResultsThe mean angles between each of the axes defined by the fibula and the tibial crest with the mechanical axis were 2.9° ± 0.6° of valgus and 0.7° ± 0.9° of varus in the coronal plane and 2.2° ± 0.8° of posterior and 3.6° ± 1.0° of anterior inclination in the sagittal plane. The middle one-third of the tibial crest (TCL) was revealed as a useful landmark, especially in female patients, who possess TCLs that were within 3° of the tibial mechanical axis in the coronal plane. There were no patient-specific factors strongly affecting reliability of these landmarks.ConclusionsWe can use these landmarks even if the patient has tibial bowing or severe varus deformity. Although not considering soft tissue thickness, our study demonstrated that the tibial crest in the coronal and sagittal planes could be useful guidelines in performing TKAs.Level of evidenceII     

Radiographic assessment of knee–ankle alignment after total knee arthroplasty for varus and valgus knee osteoarthritis

Background

There are unanswered questions about knee–ankle alignment after total knee arthroplasty (TKA) for varus and valgus osteoarthritis (OA) of the knee. The aim of this retrospective study was to assess knee–ankle alignment after TKA.

In vivo kinematic analysis of posterior-stabilized total knee arthroplasty for the valgus knee operated by the gap-balancing technique

BackgroundMost in vivo kinematic studies of total knee arthroplasty (TKA) report on the varus knee. The objective of the present study was to evaluate in vivo kinematics of a posterior-stabilized fixed-bearing TKA operated on a valgus knee during knee bending in weight-bearing (WB) and non-weight-bearing (NWB).MethodsA total of sixteen valgus knees in 12 cases that underwent TKA with Scorpio NRG PS knee prosthesis and that were operated on using the gap balancing technique were evaluated. We evaluated the in vivo kinematics of the knee using fluoroscopy and femorotibial translation relative to the tibial tray using a 2-dimensional to 3-dimensional registration technique.ResultsThe average flexion angle was 111.3° ± 7.5° in WB and 114.9° ± 8.4° in NWB. The femoral component demonstrated a mean external rotation of 5.9° ± 5.8° in WB and 7.4° ± 5.2° in NWB. In WB and NWB, the femoral component showed a medial pivot pattern from 0° to midflexion and a bicondylar rollback pattern from midflexion to full flexion. The medial condyle moved similarly in the WB condition and in the NWB condition. The lateral condyle moved posteriorly at a slightly earlier angle during the WB condition than during the NWB condition.ConclusionsWe conclude that similar kinematics after TKA can be obtained with the gap balancing technique for the preoperative valgus deformity when compared to the kinematics of a normal knee, even though the magnitude of external rotation was small. Level of evidence: IV.     

Comparison between navigated reported position and postoperative computed tomography to evaluate accuracy in a robotic navigation system in total knee arthroplasty

BackgroundComputer navigation increases reproducibility compared to non-navigated total knee arthroplasty (TKA). Robotics navigation is a branch of computer navigation technology that might further improve accuracy of implant placement. The aim of this study is to assess the accuracy achieved in TKA with a robotic navigation system.MethodsOne hundred seventy three knees. System studied: Omni navigation System (OMNI, Raynham, MA). Navigated femoral and tibial cuts were compared to postoperative computed tomography (CT). Measurements reviewed: femoral coronal alignment (FCA), femoral sagittal alignment (FSA), femoral rotational alignment (FRA), tibial coronal alignment (TCA), tibial sagittal alignment (TSA) and hip–knee–ankle (HKA) angle. Statistical analysis was made using R.ResultsThe mean differences between the navigated reported and the CT positions were: FCA: 0.1 ± 1.2° more varus (P = 0.58), FSA: 1.5 ± 0.3° more flexed (P < 0.001), FRA: 0.0 ± 1.7° (P = 0.93), TCA: 0.7 ± 1.1° more varus (P < 0.001), TSA: − 1.3 ± 1.5 more negative slope (P < 0.001), HKA angle: 0.4 ± 2.4 more varus (P < 0.049).The percentages of concordance inside a three degree difference were: FCA: 98% (169 knees), FSA: 100% (173 knees), FRA: 94% (162 knees), TCA: 99% (171 knees), TSA: 93% (161 knees) and HKA angle: 83% (144 knees).ConclusionsThe current study showed that the robotic navigation system studied is highly accurate regarding final implant positioning for FCA, FRA and TCA. It has less accuracy in FSA, TSA and the HKA angle.     

Intraoperative assessment of midflexion laxity in total knee prosthesis

BackgroundSoft-tissue balancing of the knee is fundamental to the success of a total knee arthroplasty (TKA). In posterior-stabilized TKA, there is no stabilizer of the anterior–posterior translation in the midflexion range in which the cam-post mechanism does not engage yet. Therefore, instability in the midflexion range is suspected to occur in posterior-stabilized TKA. The purpose of this study was to measure the joint gap throughout a full range of motion and to analyze the joint gap laxity in the midflexion range after implantation of a mobile-bearing posterior-stabilized total knee prosthesis.MethodsJoint gap kinematics in 259 knees with varus osteoarthritis were measured during TKAs using a tensor device with the same shape of a total knee prosthesis of the same design was used. After the implantation of a mobile-bearing posterior-stabilized prosthesis and the reduction of the patellofemoral joint, the joint gap was measured at 0°, 30°, 60°, 90°, 120°, and 145° of flexion.ResultsThe center size of the joint gap was tight in extension and deep flexion and loose at midflexion ranges, especially at 30° of flexion (p < 0.001). The symmetry of the joint gap was varus at 0° and 145° of flexion (p < 0.001).ConclusionsOur results showed the joint gap laxity in the midflexion range after the implantation of a mobile-bearing posterior-stabilized prosthesis. Our new tensor device, which can attach the polyethylene insert trial, will provide the important information about the joint gap kinematics after implantation of total knee prostheses.Level of evidenceIV.     

Accuracy of implantation during computer-assisted minimally invasive Oxford unicompartmental knee arthroplasty: A comparison with a conventional instrumented technique

The prognosis of unicompartmental knee arthroplasty (UKA) is strongly associated with the accuracy of the component alignment. To determine the accuracy of navigated UKA during primary minimally invasive Oxford UKA, twenty-nine knees of 29 consecutive patients (Group A) implanted using conventional instrumented UKA were followed by 23 knees of 17 consecutive patients (Group B) implanted by navigation assisted UKA and radiological results regarding alignments of the femorotibial mechanical axis, femur, and tibial component were compared in the two groups. Assessments of mechanical limb alignment revealed statistically significant increases in mechanical limb alignment post-operatively in both groups (p = 0.0 for both). In terms of component alignment, Group B had more prostheses implanted in the satisfactory range (> ± 3° from the targeted values) for the femoral and tibial components than Group A. There were no significant differences in the rate of prosthesis implanted within the range of radiographic alignment variations for the coronal implantation of either femoral or tibial components in both groups. (Radiographic alignment variation; coronal orientation of femoral components 90 ± 10°, sagittal orientation of femoral components 90 ± 5°, coronal orientation of tibial components from 10° varus to 5° valgus, sagittal orientation of tibial components from 7° of posterior tibial flexion to 5° of anterior tibial flexion). However, significant increases in the accuracies of sagittal implantation of femoral and tibial components were observed in Group B versus Group A. Our data suggest that navigated implantation improves the accuracy of the radiological implantation of the Oxford UKA prosthesis without increasing complications versus conventional UKA.     

The incidence and results of manipulation after primary total knee arthroplasty

This study investigates a cohort of patients who required a manipulation after total knee arthroplasty (TKA) to determine whether there was an association between pre-TKA and post-manipulation range of motion (ROM). Thirty-seven of 800 TKAs were manipulated (4.6% incidence); complete data were available for 36 knees. The pre-TKA stiff group (< 110° total arc of motion; n = 16), on average, had 27° less arc of motion before TKA than the non-stiff group (n = 20; p < 0.001). Mean arc of motion in the stiff group was 68° before manipulation and 109° after manipulation (p < 0.001). Mean arc of motion in the non-stiff group was 80° before manipulation and 118° after manipulation (p < 0.001). Patients with pre-TKA stiffness improved from a total arc of motion of 94 to 109 (p < 0.001) while patients without pre-TKA stiffness changed from 121 to 118 (p = 0.169). In both groups, the success of TKA can still be high despite early motion loss and subsequent manipulation.     

Factors contributing to inherent varus alignment of lower limb in normal Asian adults: Role of tibial plateau inclination

PurposeThis prospective study aimed to evaluate radiographically, mechanical or hip–knee–ankle (HKA) axis in healthy, asymptomatic, Asian (Indian and Korean) adults between 20 and 40 years of age to determine the incidence of inherent varus (mechanical limb alignment of > 3° varus) and the factors influencing it.MethodsThree hundred and eighty-eight lower limbs were evaluated using full length, standing hip-to-ankle radiographs in 198 healthy, asymptomatic, Asian (Indian and Korean) adults between 20 and 40 years of age to assess the hip–knee–ankle (HKA) angle, medial proximal tibial angle (MPTA), femoral bowing and femoral neck–shaft angle to determine the incidence of inherent varus (mechanical limb alignment of > 3° varus) and the factors influencing it.ResultsOverall, the mean HKA angle was 177.6° ± 2.6° with 34.5% of limbs in inherent varus (mean HKA angle 174.9° ± 1.8°). The incidence of inherent varus was significantly higher (p = 0.01) in males (40%) compared to females (28%) but similar among Indian (34%) and Korean subjects (35%). The hip–knee–ankle (HKA) angle showed significant positive correlation (r = 0.82, p < 0.001) with only the medial proximal tibial angle (MPTA).ConclusionsInherent varus alignment of the lower limb is fairly common among asymptomatic, Asian adults. These results raise several pertinent questions regarding the role of inherent varus in the aetiopathogenesis of knee osteoarthritis and in lower limb realignment procedures.     

In vivo kinematic determination of total knee arthroplasty from squatting to standing

This study analyzed three dimensional (3D) in vivo kinematic data from the squatting to standing position for 18 Japanese subjects (18 knees) implanted with either Legacy^® Posterior Stabilized (LPS) Flex Fixed Bearing TKA or LPS Flex Mobile Bearing TKA. Under weight-bearing conditions, for all patients, the average roll-forward motions for the medial and lateral condyles were 4.0 ± 3.6 mm and 6.3 ± 3.4 mm, and the average external axial rotation was 3.1° ± 4.1°. For both groups, the weight-bearing range-of-motion (ROM) (110.7° ± 12.7°) was less than pre (127.2 ± 15.5°) and post (135.6 ± 5.4°) operative non-weight bearing ROM. As hypothesized, the incidence, average and maximum liftoff for the squatting to standing activity were much less than those of deep knee bend (DKB), and condylar motions and kinematics were opposite that of the DKB. There was little statistical difference of their kinematic patterns during this activity between the LPS fixed and mobile TKA implants.     

Do long leg supine CT scanograms correlate with weight-bearing full-length radiographs to measure lower limb coronal alignment?

IntroductionThe gold standard for measuring knee alignment is the lower limb mechanical axis (MA) using weight-bearing lower limb full-length x-ray (FLX). However, CT scanograms (CTS) are becoming increasingly popular in view of lower radiation exposure, speed of data acquisition and supine positioning. We compared the correlation and degree of agreement of knee joint coronal alignment using these two imaging modalities.MethodFrom our series of complex primary and revision knee arthroplasty patients, we selected those with both FLX and CTS recorded onto digital PACS. The coronal alignments were assessed in 24 knees and the valgus/varus angles relative to the MA were measured. Results were analysed statistically using the paired samples t-test, Pearson's correlation coefficient, intra-class correlation coefficient, Cohen's kappa and Passing and Bablok regression to assess potential equality of methods.ResultsThe mean MA was 180.5° (165°–200°) for the CTS and 181° (164°–202°) for the FLX. The CTS MA angle data between the assessors were highly correlated (r = 0.971, p < 0.001) as were FLX MA angle measurements (r = 0.988, p < 0.001). 41.7% of the CTS and 37.5% of the FLX were in varus alignment, while 50% of the CTS and 43.8% of the FLX were in valgus alignment. Malalignment > 5° was revealed by 18.8% of the CTS and 35.4% of the FLX.ConclusionOverall, good agreement was observed in MA angle data between the two imaging modalities, but reproducibility may be problematic. In the malaligned limb, weight-bearing FLX still remains a vital imaging modality. CTS should be used with caution in view of the under-detection of malalignment.     

The flexion gap preparation does not disturb the modified gap technique in posterior stabilized total knee arthroplasty

PurposePreparation of the flexion gap (resection of the posterior femoral condyle and removal of the osteophytes on the posterior aspect of the femur to re-establish the posterior capsular recess) during modified gap technique might change the soft-tissue balancing and disturb the preparation of equal and rectangular extension and flexion joint gaps. The purpose of this study was to measure the change in the extension and flexion gaps using tension device during posterior stabilized TKA with modified gap technique.MethodsWe examined changes in the extension gap and flexion gap during posterior stabilized TKA using modified gap technique in 100 consecutive varus osteoarthritis knees. The extension gap was first prepared and then the distance and angle of both extension and flexion gaps were measured before and after preparation of the flexion gap using a tension device.ResultsAlthough both the extension and flexion gaps significantly increased during the operation, the amount of the increase was very small, and the difference between the increase in the extension gap (0.9 ± 0.1 mm [mean ± SE]) and that in the flexion gap (0.7 ± 0.1 mm) was not statistically significant. Mean angular changes in extension and flexion gaps during the operation were less than 1°.ConclusionsThe preparation of the flexion gap in posterior stabilized TKA did not disturb the modified gap technique in terms of equal and rectangular extension and flexion gaps.     

Accuracy of a hand-held surgical navigation system for tibial resection in total knee arthroplasty

BackgroundAccuracy of total knee arthroplasty (TKA) implant placement and overall limb are important goals of TKA technique.MethodsThe accuracy and ease of use of an accelerometer-based hand-held navigation system for tibial resection during TKA was examined in 90 patients. Preoperative goals for sagittal alignment, navigation system assembly time, resection time, and tourniquet time were evaluated. Coronal and sagittal alignment was measured postoperatively.ResultsThe average coronal tibial component alignment was 0.43° valgus; 6.7% of patients had tibial coronal alignment outside of ± 3° varus/valgus. The difference between the intraoperative goal and radiographically measured posterior tibial slope was 0.5°. The average time to completion of the tibial cut was 4.6 minutes.ConclusionThe accelerometer-based hand-held navigation system was accurate for tibial coronal and sagittal alignment during TKA, with no additional surgical time compared with conventional instrumentation.     

Lateral parapatellar approach with tibial tubercle osteotomy for the treatment of non-correctable valgus knee osteoarthritis: A retrospective clinical study

BackgroundThe aim of this retrospective study was to evaluate the efficacy of a lateral parapatellar approach combined with a tibial tubercle osteotomy (TTO) in patients undergoing total knee arthroplasty (TKA) with non-correctable valgus knee osteoarthritis.MethodsWe studied 53 consecutive patients (57 knees) who had a primary TKA via lateral parapatellar approach with a global step-cut “coffin” type TTO over a 10-year period. All patients had non-correctable grade II valgus deformity according to the Ranawat classification. The average age of patients was 71 years (45 to 77) and the mean follow-up was 39 months (20 to 98).ResultsPost-surgery, there was a significant improvement in knee extension (p = 0.002), flexion (p = 0.006), Knee Society Pain and Function Scores (p < 0.001) and WOMAC Osteoarthritis Index (p < 0.001). The tibiofemoral angle changed from a preoperative median value of 11 deg (10 to 17) to a postoperative value of 3.75 deg (0 to 9). Congruent patellar tracking was observed in all cases. All but one osteotomy united in a median period of 16.7 weeks (9 to 28) and no hardware removal was required. One knee developed infection treated with two-stage reconstruction. A proximal tibial stress fracture also occurred in a patient on long-term bisphosphonate therapy.ConclusionLateral parapatellar approach along with TTO is an effective technique for addressing non-correctable valgus knee deformity during TKA.     

The accuracy of component alignment in custom cutting blocks compared with conventional total knee arthroplasty instrumentation: Prospective control trial

BackgroundThe purpose of this study was to assess whether custom cutting blocks improve accuracy of component alignment compared to conventional TKA instrumentation.MethodsEighty primary TKA patients were enrolled in an open-label randomized prospective clinical trial and were divided into two groups, 40 custom cutting blocks and 40 conventional TKA instrumentations. The primary outcome was prosthetic alignment with respect to mechanical axis and epicondylar axis. Secondary outcomes included operative time, 24-hour postoperative blood loss and hemoglobin at discharged.ResultsThere were no statistical significant differences in the postoperative mechanical axis between the custom cutting blocks group and conventional TKA group, (95% vs. 87.5% within 3° of neutral mechanical alignment, p = 0.192). The average rotational alignment was statistically significantly different in the custom cutting blocks group (1.0° ± 0.6° vs. 1.6° ± 1.8° external rotation from epicondylar axis, p < 0.001). There were statistical significant differences in operation time between custom cutting blocks group and conventional group, skin to skin [57.5 ± 2.3 min vs. 62.1 ± 1.5,p < 0.001]. We found an improvement in group 1 compared with group 2 regarding the proportion of patients with postoperative blood loss within 24 h.ConclusionsCustom cutting blocks technique was a surgical procedure which provided better accuracy in rotational alignment but no statistical differences in mechanical axis, less operative time and reduced blood loss than the conventional TKA instrumentation in the majority of patients.     

Satisfactory results at 8 years mean follow-up after ADVANCE® medial-pivot total knee arthroplasty

BackgroundAlthough good overall results have been reported with TKA, certain problems and limitations remain, primarily due to postoperative differences in joint kinematics, when compared with the normal knee. ADVANCE® Medial-Pivot TKA involves replicating the medial pivoting behavior observed in normal knees. Here, we aimed to investigate the clinical and radiological results and complications of TKA using this implant, at mid-term follow-up.MethodsFrom January 2001 to March 2012, we retrospectively selected 76 patients (85 knees; mean age at operation, 70.2 ± 8.1 years; range, 51–88 years) with a mean follow-up period of 93.1 ± 14.3 months (range, 72–132 months). Indications for TKA included primary degenerative osteoarthritis (60 knees), rheumatoid arthritis (22 knees), osteonecrosis (two knees), and osteoarthritis following high tibial osteotomy (one knee). The clinical and radiographic results were evaluated.ResultsKaplan–Meier survivorship analysis indicated a success rate of 98.3% (95% confidence interval, 96.6–99.9%). Comparison of pre- and postoperative knee extension angles and ranges of motion showed significant improvement postoperatively, in both the Knee Society Scores (KSS) and Knee Society Functional Scores (KSFS) (p < 0.05). In one case, radiographic assessment indicated implant loosening due to infection; however, despite this complication, significant improvement of postoperative varus or valgus deformity angles were noted in all cases (p < 0.05).ConclusionPatients undergoing ADVANCE® Medial-Pivot TKA achieved excellent clinical and radiographic results without any implant-related failures at mid-term follow-up.Level of evidence: Level IV     

Total knee arthroplasty with patient-specific instruments improves function and restores limb alignment in patients with extra-articular deformity

BackgroundRestoring function and alignment when treating knee arthritis with a total knee arthroplasty (TKA) in patients who have an extra-articular deformity (EAD) from a malunion or with retained femoral hardware is a challenge. The normal anatomical landmarks are hard to find and difficult to use to obtain correct alignment. The procedure will be further challenged by angular deformity of the femur or tibia. A retrospective study was performed on a case series of patients with EAD or obliteration of the canal treated with patient-specific instruments (PSI).MethodsA multicenter retrospective review of 10 patients with multiplanar deformities in which the knee components were aligned with patient-specific instruments was performed. Outcome and alignment were studied.ResultsAt a mean follow-up of 3.4 years, function improved from preoperative as evidenced by a mean increase in the KS pain score of 53 points, KS function score of 48 points and Oxford Score of 28 points (P < 0.05). Flexion improved from 94° +/? 11° to 112° +/? 15° (P < 0.05). Limb alignment was restored with a mean Hip-Knee-Ankle angle of 179.3° +/? 1.3° (P < 0.05). Maximum outliers were 177° to 181°. An average tourniquet time of 75 +/? 9 minutes (range, 62–83 min) was observed.ConclusionsThe use of patient-specific instrumentation systems to perform TKA in patients without access to the intramedullary canal because of EAD or fixation devices, improved function and restored limb alignment. Mechanical alignment can easily be obtained with this technique by intra-articular correction of deformities under 20°.Level of EvidenceLevel IV.