Intraoperative changes in medial joint gap after posterior femoral condylar resection,posterior osteophyte removal,and femoral component placement during primary total knee arthroplasty

Background“Mid-flexion stability” is important for superior patient satisfaction following total knee arthroplasty (TKA). Thus, it is important to control medial joint gap intraoperatively as a countermeasure. However, reports on the precise intraoperative changes in medial joint gap during TKA are scarce. This study evaluated the intraoperative changes in medial joint gap during TKA.MethodsWe studied 167 knees with varus osteoarthritis that underwent 80 cruciate-retaining (CR) and 87 posterior-stabilized (PS) TKAs between January 2018 and December 2020. We measured the intraoperative changes in medial joint gap with a tensor device at 137.5 N.ResultsThe medial joint gap after posterior femoral condylar resection was significantly increased not only at 90° of flexion but also at 0° of extension in CR and PS TKAs (p < 0.01). The medial joint gap after posterior osteophyte removal was significantly increased not only at 0° of extension but also at 90° of flexion in CR and PS TKAs (p < 0.01). The medial joint gap at 0° of extension was reduced by 0.60 mm after femoral component placement in PS TKA.ConclusionSurgeons need to pay close attention to these intraoperative changes in medial joint gap by measuring the medial joint gap before and after each procedure or assuming the changes in those values before bone cutting to achieve superior patient satisfaction following TKA.     

Interobserver agreement of sensor-derived compartmental pressure measurements in computer-assisted total knee arthroplasty

BackgroundSensor-guided compartmental pressure measurements are becoming increasingly utilized in total knee arthroplasty (TKA) to objectively confirm intraoperative knee balance. We aimed to determine agreement of pressure measurements between two observers when performing sensor-guided TKA with the use of computer-assisted surgery (CAS).MethodsOne-hundred and eighteen consecutive patients undergoing 130 TKAs were analysed. Femoral and tibial trial implants were inserted prior to performing knee balancing. We compared the reliability of sensor pressure compartmental measurements between two observers at 10, 45 and 90° of flexion using intraclass correlation coefficient (ICC) estimates and the 95% limits of agreement (Bland–Altman plots).ResultsThe interobserver agreement between sensor pressure measurements was excellent at 10° of knee flexion, with ICCs of 0.93 and 0.91 in the medial and lateral compartments, respectively (P < 0.001). At 45°, medial and lateral compartment ICCs were 0.91 and 0.76, respectively (P < 0.001). At 90°, the ICC was 0.88 medially and 0.76 laterally (P < 0.001). Although the agreement decreased at higher knee flexion, it remained good to excellent. The 95% limits of agreement at each angle were all within 20 psi and 11 psi for the medial and lateral compartments, respectively.ConclusionsThere was excellent interobserver agreement of sensor pressure measurements at 10° of knee flexion with computer-assisted TKA. Interobserver agreement decreased slightly as knee flexion angles increased, particularly in the lateral compartment. It is likely that interobserver agreement and hence reliability of sensor pressure measurements in TKA has some dependence on accurate angular positioning of the knee.     

Comparison of intraoperative soft tissue balance measurement between two tensor systems in total knee arthroplasty

BackgroundDifferences in measurement outcomes using different tensors in total knee arthroplasty (TKA) remain unknown. This study aimed to compare intraoperative soft tissue balance between two measurement systems in TKA.MethodsThis study included 24 cruciate-retaining (CR) and 27 posterior-stabilized (PS) TKAs for varus-type osteoarthritis. All TKAs were performed with the measured resection technique. Intraoperative soft tissue balance was assessed with femoral component placement and patellofemoral joint reduction throughout the range of motion. Measurements were performed using the Offset Repo-Tensor (Zimmer) and Ligament Sensor Tensor (Depuy). Joint component gaps and varus/valgus ligament balance were compared statistically in CR and PS TKAs.ResultsJoint component gaps with the Offset Repo-Tensor were significantly larger at 0°, 10°, 30°, and 60° of knee flexion in CR TKA and at all knee flexion angles, except 0° and 135°, in PS TKA than those with the Ligament Sensor Tensor (P < .05). Varus balance with the Offset Repo-Tensor was significantly larger at 0°, 10°, and 30° of knee flexion in CR TKA and at 10°, 30°, 60°, 90°, and 120° of knee flexion in PS TKA than that with the Ligament Sensor Tensor (P < .05).ConclusionSurgeons should consider the discrepancy in assessing intraoperative soft tissue balance depending on the tensor used. The Ligament Sensor Tensor tended to underestimate soft tissue balance in CR and PS TKAs compared with the Offset Repo-Tensor, especially in PS TKA. Thus, surgeons should know the difference in values between the offset-type tensor with consistent distraction force and a spring-loaded tensor.     

The medial gap is a reliable indicator for intraoperative soft tissue balancing in posterior-stabilized total knee arthroplasty

BackgroundAppropriate soft tissue balance and accurate alignment are important for successful total knee arthroplasty (TKA). However, the optimal technique for establishing and measuring soft tissue balancing remains unclear. The aim of this study was to analyze the intraoperative medial and lateral gap pattern using digital knee balancer in posterior-stabilized (PS) TKA.MethodsThis study involved 55 patients with medial osteoarthritis who underwent a primary TKA using an image-free navigation system. The extension gap and the flexion gap at 90° knee flexion were assessed using an offset seesaw-type digital balancer. Continuous joint distraction force from 10 lb to 60 lb was applied. Medial gap, lateral gap, and varus angle were measured.ResultsThe medial bone gap difference between extension and flexion was constant regardless of the distraction force from 20 lb to 60 lb. The lateral bone gap was significantly greater than the medial bone gap in extension and flexion from 30 lb to 60 lb (P < 0.05). The varus angle changed depending on the distraction force, especially in flexion. The varus angle in flexion was significantly greater than that in extension from 40 lb to 60 lb (P < 0.05).ConclusionsThe medial bone gap is a reliable indicator unaffected by the distraction force during surgery and is useful for adjusting the medial gap in extension and flexion appropriately to ensure medial stability in PS-TKA. The digital knee balancer and navigation system support both precise gap assessment and surgery.     

Clinical usefulness and safety in the early phase after a newly designed rotating-platform total knee arthroplasty: A prospective multicentre cohort study with a 2-year follow up

BackgroundThis study aimed to assess the clinical results and safety of a newly designed rotating-platform posterior-stabilised total knee arthroplasty (TKA) in the early postoperative phase, within 2 years of follow up.MethodsThis prospective, multicentre cohort study included 100 consecutive patients who underwent rotating-platform posterior-stabilised (PS) TKA (Vanguard PSRP). After excluding dropouts, 93 patients were analysed. The objective Knee Society Score (KSS)-2011, subjective KSS-2011, knee range of motion, EuroQol 5 Dimension index, complications, and survival rates were assessed before TKA and at 6 months, 1 year, and 2 years postoperatively. The scores at each time-point were compared, and the survival rate was assessed with revision as the endpoint. To demonstrate non-inferiority, the clinical outcomes of patients who underwent rotating-platform PS TKA were compared with those collected retrospectively from 50 patients who underwent fixed-PS TKA (Vanguard PS), defined as the control group.ResultsAll clinical outcomes at the final follow up significantly improved compared with their preoperative values (P < 0.001). The objective KSS-2011 was 90.0 ± 8.2 points, subjective KSS-2011 satisfaction was 30.7 ± 8.6 points, expectation was 10.4 ± 2.1 points, and functional activity was 74.0 ± 18.5 points at 2 years postoperatively. Complications included knee dislocation in one patient and surgical site infection in one patient. The survival rate was 99% at 2 years postoperatively. Clinical outcomes, complications, and survival rates of newly designed TKA were not statistically different compared with the control group.ConclusionThe newly designed rotating-platform PS TKA showed good clinical results and suitable safety during the early postoperative phase in this prospective multicentre cohort study.     

Is it possible to predict the final component gap in flexion before femoral posterior condylar osteotomy in cruciate-retaining and posterior-stabilized total knee arthroplasty?

BackgroundIn total knee arthroplasty (TKA) with posterior condylar osteotomy using anatomical landmarks, predicting the final flexion gap is impossible, as it differs with the presence or absence of the posterior cruciate ligament. We compared the predicted flexion gap, based on pre-femoral posterior condylar osteotomy measurements, with the postsurgical final flexion gap in cruciate-retaining (CR) and posterior-stabilized (PS) TKA.MethodsOne hundred knees of patients with osteoarthritis were included: 35 underwent CR, and 65 PS TKA. Distal femoral and proximal tibial osteotomy using the measured resection technique was performed. An anterior and posterior femoral osteotomy guide was set parallel to the surgical epicondylar axis, and the predicted flexion gap was measured using a seesaw tensor attached to the guide. After all procedures, the final component gap in flexion was measured using a similar seesaw tensor at the patella reduction position and was compared with the predicted gap.ResultsThe correlation coefficients for predicted vs. final component gap were 0.45 (P < 0.05) in CR and 0.82 (P < 0.001) in PS. The mean differences between predicted and final gaps were 1.8 mm for CR and 1.0 mm for PS. In 34.3% of CR cases, the gap difference was more than 2 mm.ConclusionIt is possible to predict the final flexion gap before femoral posterior condylar osteotomy, with a strong correlation observed between predicted and final component gaps in PS TKA. However, in CR, more than 30% of the cases showed unexpectedly large final flexion gaps.     

CR假体与PS假体全膝关节置换治疗膝骨性关节炎合并膝外翻畸形的疗效分析

目的 比较后交叉韧带保留型（CR）假体与后方稳定型（PS）假体行人工全膝关节置换术（TKA）治疗膝骨性关节炎合并膝外翻畸形的临床疗效。方法 回顾性分析南昌大学附属赣州医院关节外科2019年5月至2021年5月收治的60例（60膝）膝骨性关节炎合并膝外翻畸形患者资料,均为单侧置换。30例采用CR假体行TKA治疗（CR组）,30例采用PS假体行TKA治疗（PS组）。比较两组患者的手术时间、术中失血量、术后引流量、术后3 d血红蛋白（Hb）下降量及深静脉血栓发生情况;比较两组患者手术前后膝外翻角;比较两组患者术后1周、1个月、3个月、6个月、1年疼痛视觉模拟评分（VAS）、膝关节活动度（ROM）、美国特种外科医院膝关节评分（HSS）。结果 60例患者均顺利完成TKA手术,所有患者随访13 ～ 28个月,平均（18.51±0.90）个月。CR组术中出血量、术后引流量、术后3 d的Hb下降量较PS组减少（P＜0.05）;两组手术时间相当、术后均无深静脉血栓发生,差异无统计学意义（P＞0.05）;两组手术前后膝外翻角的比较差异无统计学意义（P＞0.05）;CR组术后1周、1个月VAS评分较PS组更低（P＜0.05）,两组术后3个月、6月、1年VAS评分比较差异无统计学意义（P＞0.05）;CR组术后1周、1个月、3个月膝关节ROM和HSS评分优于PS组（P＜0.05）,两组术后6个月、1年膝关节ROM和HSS评分比较差异无统计学意义（P＞0.05）。结论 采用CR或PS假体行TKA手术治疗膝骨性关节炎合并膝外翻畸形均可有效纠正膝关节畸形、减轻膝关节疼痛、改善膝关节活动度及功能,取得满意临床疗效;但相对PS假体,CR假体保留了后交叉韧带,减少了股骨髁部截骨量,从而减少手术出血,更好减轻早期术后疼痛,有助于TKA术后早期功能康复。     

Under-correction of preoperative varus alignment does not lead to a difference in in-vivo bone loading in 3D-SPECT/CT compared to neutral alignment

BackgroundThe aim was to investigate the correlation of bone tracer uptake (BTU) in SPECT/CT and changes in coronal knee alignment after total knee arthroplasty (TKA). We questioned if undercorrection of preoperative varus alignment leads to a difference in BTU compared to neutral alignment.MethodsConsecutive 66 patients who received SPECT/CT before and after TKA were retrospectively included. Adjusted mechanical alignment was the alignment target. The alignment of the knee was measured on 3D-CT by selecting standardized landmarks. Maximum (mean ± SD) and relative BTU (ratio to the reference) were recorded using a previously validated localization scheme (p < 0.05).ResultsIn the native group, 20 knees were aligned (30.3%) in valgus (HKA > 181.5°), 12 (18.2%) in neutral (178.5°-181.5°) and 34 (51.5%) in varus (HKA < 178°). Overall TKA changed the alignment towards neutral. 48.5% remained in the same groups, whereas 50% of native valgus and 33% of varus knees changed to neutral after TKA. In native varus alignment mean BTU was significantly higher in some medial tibial and femoral regions (fem1ia (p = 0.010), fem1ip (p = 0.002), tib1a.mid (p = 0.005), tib1a.tray (p = 0.000), tib1p.tray (p = 0.000)); in native valgus alignment mean BTU was higher in the corresponding lateral tibial and femoral regions (fem2ip (p = 0.001), tib2a.tray (p = 0.011), tib2p.tray (p = 0.002)). After TKA, a significant decrease in femoral and tibial BTU (femoral preoperative BTU 1.64 +/-0.69; femoral postoperative BTU 0.95 +/-0.42; p = 0.000// tibial preoperative BTU 1.65 +/- 0.93; tibial postoperative BTU 1.16 +/- 0.48; p = 0.000) and an increase in patellar BTU was observed (p = 0.025). Native varus alignment correlated with a higher medial BTU decrease medially. Undercorrection of preoperative varus alignment showed no higher BTU after TKA.ConclusionPreoperative varus alignment correlated with a higher decrease in BTU in specific femoral and tibial medial regions. Preoperative valgus alignment correlated with a higher decrease in the corresponding lateral regions. Undercorrection of preoperative varus alignment did not lead to higher bone loading reflected by BTU 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.     

Three-dimensional morphology of the distal femur based on surgical epicondylar axis in the normal elderly population

BackgroundWe aimed to analyze the surface morphology of the distal femur in three dimensions for the healthy elderly, based on the concept that the surgical epicondylar axis (SEA) is a better surrogate for the flexion–extension axis of the knee joint.MethodsWe studied 77 healthy elderly volunteers (40 males and 37 females; age, 68 ± 6 years). The medial and lateral contact lines were calculated three-dimensionally, using the highest points of the medial and lateral condyles in 201 cross-sectional planes around the SEA (every 1°, −60° (hyperextension) to 140° (flexion)). A piecewise fitting function consisting of two linear segments was applied to detect the inflection point of the constant radii in the sagittal plane. The main assessment parameters were knee flexion angle at the inflection point of the radius (inflection angle), mean radius from 0° to the inflection angle (constant radius), and coronal tilt angle of the contact line.ResultsThe inflection angles, constant radii, and coronal tilt angles were 78.2 ± 8.6°, 26.1 ± 2.3 mm, and −0.6 ± 3.2° and 65.6 ± 9.2°, 23.9 ± 2.2 mm, and 6.2 ± 3.2° in the medial and lateral condyles, respectively (all, P < 0.001). The coronal alignment was 88.7 ± 2.2°.ConclusionsThe medial and lateral femoral condyles showed asymmetrical morphologies with the almost ‘constant’ radius of sagittal curvature from 0° to around 80° and 65° of knee flexion, respectively.     

Patellar resurfacing has minimal impact on in vitro tibiofemoral kinematics during deep knee flexion in total knee arthroplasty

BackgroundWhile patellar resurfacing can affect patellofemoral kinematics, the effect on tibiofemoral kinematics is unknown. We hypothesized that patellar resurfacing would affect tibiofemoral kinematics during deep knee flexion due to biomechanical alteration of the extensor mechanism.MethodsWe performed cruciate-retaining TKA in fresh-frozen human cadaveric knees (N = 5) and recorded fluoroscopic kinematics during deep knee flexion before and after the patellar resurfacing. To simulate deep knee flexion, cadaver knees were tested on a dynamic, quadriceps-driven, closed-kinetic chain simulator based on the Oxford knee rig design under loads equivalent to stair climbing. To measure knee kinematics, a 2-dimensional to 3-dimensional fluoroscopic registration technique was used. Component rotation, varus-valgus angle, and anteroposterior translation of medial and lateral contact points of the femoral component relative to the tibial component were calculated over the range of flexion.ResultsThere were no significant differences in femoral component external rotation (before patellar resurfacing: 6.6 ± 2.3°, after patellar resurfacing: 7.2 ± 1.8°, p = 0.36), and less than 1° difference in femorotibial varus-valgus angle between patellar resurfacing and non-resurfacing (p = 0.01). For both conditions, the medial and lateral femorotibial contact points moved posteriorly from 0° to 30° of flexion, but not beyond 30° of flexion. At 10° of flexion, after patellar resurfacing, the medial contact point was more anteriorly located than before patellar resurfacing.ConclusionDespite the potential for alteration of the knee extensor biomechanics, patellar resurfacing had minimal effect on tibiofemoral kinematics. Patellar resurfacing, if performed adequately, is unlikely to affect postoperative knee function.     

Modern femoral component design in total knee arthroplasty shows a lower patellar contact force during knee flexion compared with its predecessor

BackgroundThe relationship between the femoral component design in total knee arthroplasty (TKA) and the patellofemoral contact force, as well as the soft tissue balance, has not been well reported thus far.MethodsTwenty-eight mobile-bearing posterior-stabilized (PS) TKAs using the traditional model (PFC Sigma) and 27 mobile-bearing PS TKAs using the latest model (Attune) were included. Surgeries were performed using the measured resection technique assisted with the computed tomography (CT)-based free-hand navigation system. After all the trial components were placed, patellar contact forces on the medial and lateral sides were measured using two uniaxial ultrathin force transducers with the knee at 0°, 10°, 30°, 60°, 90°, 120°, and 135° of flexion. The joint component gap and the varus ligament balance of the femorotibial joint were also measured. The non-paired Student’s t-test was conducted to compare the values of the two groups.ResultsThe medial patellar contact force was significantly lower for Attune group than for PFC Sigma group at 120° of knee flexion (P = 0.0058). The lateral patellar contact force was also significantly lower for Attune group than PFC Sigma group at 120° and 135° of knee flexion (P = 0.0068 and P = 0.036). The joint component gap, as well as the varus ligament balance, showed no statistically significant difference between the two groups.ConclusionsReduced thickness and width of the anterior flange of the femoral component in the Attune may play a role in low patellar contact force.     

Gait modification with subject-specific foot progression angle in people with moderate knee osteoarthritis: Investigation of knee adduction moment and muscle activity

BackgroundSubject-specific foot progression angle (SSFPA) as a personalized gait modification is a novel approach to specifically reducing knee adduction.ObjectiveThis study aimed to investigate the effect of gait modification with SSFPA on the knee adduction moment and muscle activity in people with moderate knee osteoarthritis (KOA).MethodsIn this clinical trial, nineteen volunteers with moderate KOA were instructed to walk in four different foot progression angle conditions (5° toe-out, 10° toe-out, 5° toe-in, and 10° toe-in) to determine SSFPA that caused the greatest reduction in the greater peak of the knee adduction moment (PKAM). Immediately and after 30 minutes of gait modification with SSFPA, peak root means square (PRMS) and medial and lateral co-contraction index (CCI) were evaluated in the knee muscles.ResultWalking with 10° toe-in showed the most reduction in the greater PKAM (17.52 ± 15.39%) compared to 5° toe-in (7.1 ± 19.14%), 10° toe-out (1.26 ± 23.13%), and 5° toe-out (7.64 ± 16.71%). As the immediate effect, walking with SSFPA caused a 20.71 ± 12.07% reduction in the greater PKAM than the basic FPA (p < 0.001). After 30 minutes of gait retraining, the greater PKAM decreased by 10.36 ± 26.24%, but this reduction was not significant (p = 0.17). In addition, PRMS of lateral gastrocnemius increased (p = 0.04), and lateral CCI increased 10.72% during late stance (p = 0.04).ConclusionOur findings suggest the immediate effect of gait modification with SSFPA on decreasing the knee adduction moment. After gait retraining with SSFPA, the increase of lateral muscle co-contraction may enhance lateral knee muscle co-activity to unload the medial knee compartment.Clinical Trial Register Number: IRCT20101017004952N8.     

A greater reduction in the distal femoral anterior condyle improves flexion after total knee arthroplasty in patients with osteoarthritis

BackgroundThe effect of an anterior condylar height (ACH) change after total knee arthroplasty (TKA) is not well-known. The effect of an ACH change was evaluated on postoperative knee flexion, New Knee Society Scores (2011KSS), and patellofemoral contact force.MethodsThe study included 101 knees that underwent TKA. The medial or lateral ACH was measured using pre-operative and postoperative computed tomography. Pearson correlation between the change in ACH and knee flexion was calculated. The determinant of the change in flexion was evaluated using multivariable linear regression. The association between ACH and 2011KSS was assessed. Using the cases with the three highest and three lowest pre-operative medial ACHs, computer simulation was performed to detect the changes in patellofemoral contact forces.ResultsA postoperative reduction in ACH correlated with increased flexion at one year (medial ACH, R = 0.58; lateral ACH, R = 0.48). On multivariable linear regression, reductions in medial ACH (β = 1.7, P < 0.001) and pre-operative flexion (β = ? 0.3, P < 0.001) were associated with increased flexion. A decrease in ACH was associated with improvements in advanced activities (medial, R² = 0.06; lateral, R² = 0.08) in 2011KSS. On computer simulation, all three cases with reduced and increased medial ACHs showed decreased and increased patellofemoral contact forces, respectively.ConclusionsA change in ACH was an independent predictor of knee flexion after TKA. Greater reduction in ACH was associated with improved flexion after TKA, whereas an increase in postoperative ACH may be a risk factor for flexion loss.     

Long-term results of revision total knee arthroplasty using a rotating hinge implant

BackgroundRotating hinge implants are commonly used in revision total knee arthroplasty (TKA) in the setting of significant ligamentous instability or bone deficiency. These highly constrained implants have been associated with variable clinical outcomes and uncertain long-term survivorship. The aim of this study is to establish long-term functional outcomes, radiographic results, and survivorship after revision TKA with a rotating hinge implant.MethodThis is a retrospective study of prospectively collected data of 41 consecutive patients undergoing revision TKA with rotating hinge components and minimum 10-years follow-up. The study included 22 females (53.7%) and 19 males (46.3%) with a mean age of 66.6 ± 8.5 years. Clinical outcomes recorded included the Oxford Knee Score (OKS) preoperatively and at latest follow-up. Range of motion, implant survivorship, and complications were also recorded. Predefined radiological outcomes were obtained using plain radiographs.ResultsThere was a significant improvement in OKS after revision TKA with a rotating hinge implant compared to preoperative scores (40.7 ± 4.2 vs. 21.4 ± 4.9 respectively, p < 0.001). At latest follow-up, mean range of motion was 111.5° ± 9.3° and mean overall limb alignment was 0.2° ± 2.0° varus. Implant survivorship at minimum 10-year follow-up was 90.2%. Radiographic lucent lines were observed in 14 patients (34.1%).ConclusionRevision TKA with a rotating hinge implant leads to satisfactory clinical outcomes and very good implant survivorship at long-term follow-up. Surgeons should have a low threshold to use these versatile implants in complex revision knee arthroplasty.     

Postoperative outcomes of total knee arthroplasty compared to unicompartmental knee arthroplasty: A matched comparison

BackgroundThe purpose of this study was to evaluate early postoperative outcomes in patients following UKA (unicompartmental knee arthroplasty) compared to a matched cohort of TKA (total knee arthroplasty) patients.MethodsPatients who met radiographic criteria for a medial UKA who underwent either a TKA or UKA at a single institution were matched based on age, gender, and BMI.ResultsOne hundredy and fifty UKA in 138 patients and 150 TKA in 148 patients were included in this retrospective analysis. Mean age was 62.6 ± 9 years and 65.2 ± 9 years in the UKA and TKA groups respectively (p = .01). Patients who underwent UKA had significantly less pain at two and six weeks postoperatively compared to TKA patients with mean Numeric Pain Rating Scale (NPRS) scores of 3.7 ± 1.1 vs. 7.8 ± 1.2, p < .001 and 2.6 ± 1.3 vs. 4.6 ± 1.6, p < .001 respectively. Knee Society Scores (KSS) were higher in the UKA group at six weeks and two years postoperative (86.5 ± 2.8 vs. 81.4 ± 3.6, p < .001 and 89.5 ± 2.4 vs. 84.5 ± 3.3, p < .001 respectively). Return to work was faster in the UKA group (mean 20.6 ± 7.89 vs. 38.6 ± 6.23 days, p < .001). The UKA group also had higher mean Forgotten Joint Scores of 90.5 ± 3.6 vs. 79.5 ± 9.5 (p < .001).ConclusionsPatients with primarily medial compartment OA who underwent UKA had less postoperative pain, earlier return to work, and higher KSS compared to a matched group who underwent TKA.     

术中应用不同假体对全膝关节置换术后引流的影响

目的 探讨术中使用后方稳定型（posterior cruciate stabilization, PS）与后交叉韧带保留型（posterior cruciate retention, CR）假体对全膝关节置换术（total knee arthroplasty, TKA）术后引流的影响。方法 回顾性分析2018年6月至2018年10月终末期骨性关节炎行全膝关节置换的患者102例，其中62例采用后交叉韧带保留型（CR）假体（CR组），40例采用后稳定型（PS）假体（PS组）。所有患者术中均使用止血带、关节腔注射氨甲环酸（tranexamic acid, TXA），术后患肢屈曲1 h、引流管夹毕1 h、患肢冰敷24 h。收集术后2、4、24、48 h引流量和引流液中血红蛋白（hemoglobin, HB）含量，以及术后2、24、48 h静脉血中的血红蛋白（HB）含量。统计术后输血情况、早期感染并发症例数。结果 102例患者随访3个月，术后总引流量CR组（292.9±128.3）mL比PS组引流量为（355.2±136.8）mL少，两组比较差异有统计学意义（P＜0.05）。术后1 d的CR组的引流量比PS组少，两组比较差异有统计学意义（P＜0.05）。术后24 h的CR组引流液中血红蛋白含量比PS组明显下降，两组比较差异有统计学意义（P＜0.05）。术后24、48 h的PS组静脉血中血红蛋白含量比CR组明显下降，两组比较差异有统计学意义（P＜0.05）。CR组2例输了2 U红细胞，PS组2例输了1 U红细胞、9例输了2 U红细胞。102例患者术后早期均未出现感染并发症。结论 与PS假体相比，采用CR假体可减少患者的失血量、术后引流量少、降低全膝关节置换术后贫血的发生、减少围术期输血率。     

Periprosthetic joint infection after primary TKA in the medicare population: How frequently are patients revised at a different hospital?

BackgroundPeriprosthetic infection (PJI) after total knee arthroplasty (TKA) places a significant burden on hospitals. We sought to describe the proportion of patients undergoing revision for PJI at a different hospital within one year of primary TKA and whether patient characteristics or hospital volume were associated with this change.MethodsMedicare data from 2005 to 2014 was retrospectively reviewed using PearlDiver. All patients over 64 years undergoing revision for PJI within one year of primary TKA were stratified by the revision occurring within 90 days. Hospitals were grouped by annual TKA volume as Low (<50), Medium (51–100), High (101–200), and Very High (>200). Associations of patient characteristics and hospital volume with revision at a different hospital were assessed using Chi-squared tests and Somers' D.ResultsOf 8,337 patients undergoing revision within 90 days of TKA, 1,370 (16%) were revised at a different hospital. Changing hospitals was associated with having primary TKA at a lower volume hospital (24% for low, 15% medium, 12% high, and 12% very high; P < 0.001). Of 7,608 patients undergoing revision between 91 and 365 days, 1,110 (15%) were revised at a different hospital. Changing hospitals was associated with having primary TKA at a lower volume hospital (26% for low, 14% medium, 10% high, and 9% very high; P < 0.001). Changing hospitals was not associated with sex or age.ConclusionPatients frequently undergo revision for PJI at a different hospital, even within 90 days of TKA. Further research is needed to understand these implications of this care pathway shift.     

Medial peg position of cementless porous tantalum tibial component affects bone mineral density around the prosthesis after total knee arthroplasty: 2-year follow-up study

BackgroundUse of a porous tantalum tibial component for total knee arthroplasty (TKA) was reported to have beneficial effects on periprosthetic bone mineral density (BMD). In some cases, hexagonal peg is placed close to or in contact with the tibial cortex, which may result in stress-shielding around the peg. However, no studies have analyzed the relationship between peg position and BMD. The aim of this study was to compare the peg position and BMD around the peg in a porous tantalum tibial component after TKA.MethodsTwenty-seven patients (27 knees) who underwent primary TKA with a cementless porous tantalum tibial component were investigated. BMD was measured by dual-energy X-ray absorptiometry for 2 years after the operation. The distance between the peg and the tibial cortex (peg distance) was measured on the medial and lateral sides.ResultsBMD was decreased in the medial region after the operation (p < 0.01). Relative change in BMD was lower in the medial region than in the central and lateral regions (p < 0.01). Multiple regression analysis showed that medial peg distance was negatively correlated with relative change of BMD in the medial part of the tibia (p = 0.04, R = 0.402).ConclusionsThe medial peg position affected the postoperative relative change of BMD in the medial part of the tibia, but did not affect the longevity of the implant. As the tibial medial peg became closer to the medial tibial cortex, the BMD loss became larger in the medial part of the tibia at 2 years postoperatively.