Effects of posterior condylar osteophytes on gap balancing in computer-assisted total knee arthroplasty with posterior cruciate ligament sacrifice

Objective

Gap planning in navigated total knee arthroplasty (TKA) is a critical concern. Osteophytes are normally removed prior to gap planning, with the exception of posterior condylar osteophytes of the femur, which are removed after posterior condylar resection. This study investigated how posterior condylar osteophytes affect gap balancing during surgery.

Methods

This prospective study was conducted on 40 primary varus osteoarthritic knees with a posterior condylar osteophyte that underwent TKA navigation. For all knees, computed tomography (CT) was performed to evaluate osteophyte position. The extension gap and flexion gap were determined under navigation using a tension device with a distraction force of 44 lb. The extension gap and flexion gap were measured before and after osteophyte removal.

Results

This study revealed that the average osteophyte thickness after removal was 7.75 ± 5.34 mm. The average extension gap change was 0.64 ± 0.80 mm, and the average flexion gap change was 0.85 ± 1.12 mm. With respect to increases in the medial extension gap, lateral extension gap, medial flexion gap and lateral flexion gap, the average effects of posterior condylar osteophyte removal were 0.74 ± 0.81 mm, 0.53 ± 0.96 mm, 0.71 ± 0.97 mm and 1.00 ± 1.41 mm, respectively. Posterior condylar osteophyte thickness was also significantly associated with increases in the lateral extension gap (R² = 0.107, p = 0.03), medial flexion gap (R² = 0.101, p = 0.04) and lateral flexion gap (R² = 0.107, p = 0.04).

Conclusion

These results indicated that posterior condylar osteophytes of the femur affect gap balancing during TKA navigation.

     

Evaluation of joint laxity against distal traction force upon flexion in cruciate-retaining and posterior-stabilized total knee arthroplasty

Background  Several studies have reported varus-valgus stability in the extension position after total knee arthroplasty (TKA). However, few studies have evaluated joint laxity in the flexion position postoperatively. The purpose of the study was to evaluate joint laxity against distal traction force on flexion after cruciate-retaining and posterior-stabilized total knee arthroplasties. Methods  A total of 44 knees (22 knees cruciate-retaining, 22 knees posterior-stabilized) in 40 patients with osteoarthritis were tested in this study. The subjects were seated at a table and their knee joints were fixed at 80° of flexion to avoid overlapping images of condyles and the femoral shaft. Tibial shafts were adjusted to be parallel to the radiographic films, and posteroanterior radiographs were obtained. Flexion stress tests were performed with a distal traction of 100 N at a neutral foot position. Radiographs were obtained at neutral and traction positions. The distance from the perpendicular line of the top of the polyethylene insert to the midpoint on the tangential line of the femoral condyle was measured (joint space distance) at each side. Results  In the flexion-neutral position, average joint space distances were 0.1 ± 0.2 mm in cruciate-retaining (CR) TKA knees and 0.2 ± 0.3 mm in posterior-stabilized (PS) TKA knees. With flexion-traction stress tests, the average joint space distances were 0.5 ± 0. 5 mm in CR TKA knees 2.4 ± 1.2 mm in PS TKA knees. Average changes of joint space distances between the two positions were 0.3 ± 0.4 mm (CR TKA) and 2.2 ± 1.5 mm (PS TKA). The changes in joint space distances between neutral and traction positions of PS TKA knees were significantly larger than those of CR TKA knees in flexion stress tests (P < 0.01). Conclusion  The posterior cruciate ligament acted as a stabilizer against distal traction force in the CR-TKA knees. However, the laxity of PS-TKA knees against distal force differed among individual cases.     

Outcome of Revision Surgery for the Idiopathic Stiff Total Knee Arthroplasty

BackgroundIdiopathic stiff total knee arthroplasty (TKA) represents one of the most challenging subsets of the stiff TKA, as the etiology is unknown and there is no consensus on the most appropriate surgical treatment modality. Therefore, the aim of this study is to report on postoperative outcomes of revision surgery for idiopathic stiff TKA.MethodsWe retrospectively reviewed 189 consecutive patients (202 knees) who underwent revision TKA for stiffness: (1) 101 knees in the idiopathic stiffness cohort and (2) 88 in the non-idiopathic stiffness cohort. In the idiopathic stiffness cohort, 42 knees underwent isolated tibial insert exchange and 59 knees underwent component revision. Perioperative knee range of movement and complications were analyzed.ResultsThe overall revision surgery outcomes of the idiopathic stiffness cohort were worse than those of the non-idiopathic stiffness cohort with regard to maximum flexion (91.7° vs 100.1°, P = .02) and flexion range of motion (ROM) (87.6° vs 97.1°, P = .01). In the idiopathic stiffness cohort, isolated tibial insert exchange demonstrated greater maximum flexion (96.8° vs 88.4°, P = .06) and flexion ROM (93.2° vs 83.9°, P = .07). In terms of re-revision rates, the isolated tibial insert exchange idiopathic stiffness cohort demonstrated lower re-revision rates compared to the component revision idiopathic stiffness cohort (16.7% vs 31.0%, P = .01).ConclusionThis study demonstrates that the overall revision surgery outcome of idiopathic stiff TKA is worse than non-idiopathic TKA stiffness. In idiopathic stiffness cohorts, isolated tibial insert exchange was associated with lower re-revision rates than component revision, with similar efficacy in improving ROM, suggesting that isolated tibial insert exchange may be a preferred surgical treatment option in TKA patients with idiopathic stiffness.     

Changes in postoperative extension angle after total knee arthroplasty: Effect of polyethylene insert thickness

BackgroundFlexion contracture is a serious complication after total knee arthroplasty (TKA). Polyethylene insert (PE) thicker than the extension gap during surgery causes flexion contracture. The purpose of this study was to identify the changes over time in postoperative extension angle and the correlation between extension gap and PE thickness.MethodsOverall, 127 knees were analyzed to evaluate the changes in extension angle over time. “Gap difference” was defined as the distance obtained by subtracting the extension gap from the PE thickness. Patients were divided into four groups according to gap difference (0–3 or greater mm). We evaluated the correlation of gap difference and changes in postoperative extension angle over time.ResultsThe extension angles of all knees were ?4.2 ± 3.9 (deg. mean ± s.d.) at surgery, ?5.9 ± 5.7 at 3 months, ?3.4 ± 5.4 at 6 months, and ?1.3 ± 5.4 at 2 years. Gap difference was negatively correlated with the extension angle at surgery and at 2 years (r = 0.40, r = 0.36). The extension angles at 2 years in each group (groups 0, 1, 2, 3 or greater) were 2.0°±4.7°, ?0.8°±5.3°, ?3.4°±5.3°, ?4.0°±4.1° (p < 0.05), respectively.ConclusionsThe extension angle became worse at 3 months compared to that at surgery (p = 0.01) and then improved until 2 years. The correlation between gap difference and extension angle was maintained at 2 years, and thicker PE caused flexion contracture even after 2 years. Hence, PE selection considering the extension gap is important.     

Asymmetry of mediolateral laxity of the normal knee

Background Understanding the normal kinematics of the joints is important for reconstructive surgery. However, only a few extensive studies have been done on medial and lateral laxity of the normal knee. Methods Radiographs of 50 normal knees were obtained under varus and valgus stress in both extension and flexion and the relative angle of the articular surface was measured. Results In extension, the mean angle was 4.9° in varus stress and 2.4° in valgus stress. In flexion, the mean angle was 4.8° in varus stress and 1.7° in valgus stress. Lateral laxity was significantly greater than medial laxity in both extension and flexion. Conclusions Lateral laxity may be necessary for the medial pivot movement of the normal knee. There is some disagreement regarding the importance of pursuing the perfect rectangular gaps during total knee arthroplasty (TKA). The methods for measuring the tension of soft tissues during the operation are not accurate and do not always reflect the postoperative tensions of dynamic phases, such as walking and standing. Slight lateral laxity can be accepted with TKA, and further studies are necessary to determine whether prosthesis lift-off occurs in the replaced knee with slight lateral laxity similar to that in the normal knee.     

固定平台后稳定型假体全膝关节置换术后的运动学研究

 目的 探讨固定平台后稳定型假体全膝关节置换(total knee arthroplasty,TKA)术后膝关节在负重屈膝下蹲时的运动学特征。方法 选取10名健康志愿者和10例固定平台后稳定型假体TKA术后患者。制作骨骼及膝关节假体三维模型,在持续X线透视下完成负重下蹲动作,膝关节屈曲度每增加15°截取一幅图像。通过荧光透视分析技术完成三维模型与二维图像的匹配,再现股骨与胫骨在屈膝过程中的空间位置,通过连续的图像分析比较正常与固定平台后稳定型假体TKA术后膝关节在负重下蹲时股骨内、外髁前后移动及胫骨内外旋转幅度。结果 负重下蹲时,正常膝关节平均屈曲136°,股骨内、外髁分别后移(7.3±1.2) mm和(19.3±3.1) mm,胫骨平均内旋23.8°±3.4°;TKA术后膝关节平均屈曲125°,股骨内、外髁分别后移(1.4±1.6) mm和(6.4±1.7) mm,胫骨平均内旋8.5°±3.4°。结论 固定平台后稳定型假体TKA术后膝关节运动与正常膝关节相似,均表现出股骨内、外髁后移及胫骨内旋运动,但幅度小于正常膝关节,且在屈膝过程中存在股骨矛盾性前移及胫骨外旋现象。     

Primary constrained condylar knee arthroplasty in severe varus deformity: a prospective 5-year functional follow-up study in Iraqi patients

Purpose

The outcomes of the constrained condylar knee (CCK) implant used during primary total knee arthroplasty (TKA) in knees with severe varus in patients from low- and middle-income countries (LMICs) such as Iraq are not known. Hence, this study aimed to analyze and report the functional outcome of CCK TKA in patients with severe varus deformities at the end of 5 years in Iraqi patients.

Methods

In this prospective study, pre- and post-operative (at the end of 5 years) clinical outcome using Knee Society Score (KSS) and radiological deformity using hip-knee-ankle (HKA) angle was analyzed in 76 CCK TKAs (20 bilateral and 36 unilateral TKAs) performed in 56 patients with severe varus deformity (> 15°).

Results

At a mean follow-up of 60.3 months (range 60–68 months), the mean preoperative KSS knee score of 6.6 ± 4.5 improved significantly (p < 0.0001) to 87.2 ± 6.6 and the mean preoperative KSS function score of 7.1 ± 6.4 improved significantly (p < 0.0001) to 70.4 ± 7.8. The function score was good to excellent in 64.3% (36 patients), fair in 28.5% (16 patients), and poor in 7.1% (4 patients) at the end of 5 years. The mean preoperative HKA angle significantly improved (p < 0.001) from 25.5° ± 6° varus (range 17°–37°) to 3° ± 2.5° varus (range 0°–7.5°) at final follow-up.

Conclusion

The CCK implant significantly improved pain and function in patients with severe varus deformity at the end of 5 years. The CCK implant is a good option during primary TKA in severe varus knees in patients from LMICs and can help achieve clinical outcomes similar to patients from high-income countries.

     

Evaluating distal femoral torsion and posterior condylar line reliability for adjusting femoral component rotation in TKA,Egyptian population radiographic study

BackgroundFemoral component rotational alignment is critical for successful TKA. The primary study objective is to measure the preoperative distal femoral torsion (DFT) of an Egyptian patient’s cohort using a seated posteroanterior (PA) knee radiograph. The secondary objectives are to check the intraoperative reliability of using the posterior condylar line (PCL) as a reference for rotation and to measure postoperative component rotation using the same radiographic technique.Methods100 arthritic knees, 22 males, 78 females, 95 Varus and five valgus. A long anteroposterior radiograph [Hip to knee to ankle (HKA)] for coronal alignment assessment, and the anatomical posterior condylar angle (aPCA) between the anatomical transepicondylar axis (aTEA) and the PCL was measured in the seated PA knee radiographs for evaluating the DFT and component rotation. Intraoperative rotation was adjusted to 3° external rotation to the PCL.ResultsHKA improved from a preoperative mean 170.4° ± 6.2 to a postoperative mean 178.3° ± 1.5 (p < 0.005). DFT was internal in all knees; the mean aPCA was −4.5 ± 2.4 (0° to −9°), femoral component rotation significantly changed to a mean aPCA of −3.6 ± 2.3 (0° to −7°) (p = 0.005). Acceptable intraoperative patellar tracking in 94%, and patellar subluxation needed a lateral retinacular release in 2% (two valgus knees). The preoperative DFT was not affected by sex or direction of coronal deformity; more external DFT noticed in severe varus deformity.ConclusionsAll keens had an internal DFT not affected by sex, or coronal deformity direction. Using PCL as a guide to adjust femoral component rotation is a valid technique in our population.     

Two cases of late medial instability of the knee due to hip disease after total knee arthroplasty

IntroductionThere are few specific reports of late medial instability after total knee arthroplasty (TKA). We described two cases of late medial instability of the knee due to hip disease with osteoarthritis or rheumatoid arthritis after TKA, which required revision TKA.Presentation of casesAn 82-year-old woman experienced right femoral neck fracture due to a fall that required conservative treatment at age 77 years and underwent left TKA at age 80 years. A 68-year-old woman underwent left TKA at age 54 years, right TKA at age 64 years, and left THA at age 67 years. Both cases required revision TKA with constrained knee prostheses due to the severe medial instability. Hip-knee-ankle (HKA) angle, range of motion (ROM), Knee Society score (KSS) and functional score (FS) were evaluated pre- and postoperatively. Their respective HKA angle improved from 134° and 155° preoperatively to 184° and 179° postoperatively. KSS improved from −4 and 53 points to 59 and 100 points, respectively. FS improved from −10 and 58 points to 25 and 90 points, respectively. In the 82-year-old woman, ROM did not improve from −10–90° to −20–90°. On the other hand, in the 68-year-old woman, ROM improved from 0–110° to 0–125°. The late medial instability in the current case report was partly due to a similar mechanism underlying the long leg arthropathy and coxitis knee caused by hip joint degeneration.ConclusionsConstrained prostheses were applied for both patients, providing moderately good short-term results.     

Intraoperative loose flexion gap may restrict postoperative knee flexion after J-curve design posterior-stabilized total knee arthroplasty

Introduction

Although soft tissue tension during total knee arthroplasty (TKA) has been targeted to achieve equal flexion and extension gaps, such a perfect gap is not always obtained. This study was performed to investigate the impact of difference between flexion and extension gaps on postoperative knee flexion angle.

Materials and methods

We reviewed 107 consecutive TKAs using a J-curve design posterior-stabilized prosthesis. Soft tissue tension was measured intraoperatively using an offset-type tensor under 30 lb force of joint distraction with the patella reduced. All TKAs were performed in a uniform manner including the subvastus approach and without use of a pneumatic tourniquet. We assessed the association between knee flexion angle 1 year after TKA and the difference between flexion and extension gaps using Pearson’s product-moment correlation and multiple regression analysis with age, sex, body mass index, diagnosis, history of diabetes mellitus, preoperative flexion angle, and gap difference as explanatory variables.

Results

The difference between flexion and extension gaps showed a slight negative correlation with postoperative knee flexion angle in univariate analysis (r = − 0.20, 95% CI, − 0.38 to − 0.01, p = 0.04). Multiple regression analysis showed that the gap difference was an independent factor associated with postoperative knee flexion angle (β = − 0.89, 95% CI, − 1.60 to − 0.18, p = 0.01).

Conclusions

The difference between flexion and extension gaps was negatively correlated with postoperative knee flexion angle. Looser flexion gap compared with extension gap should be avoided in J-curve design posterior-stabilized TKA.

     

Gap measurement in posterior-stabilized total knee arthroplasty with or without a trial femoral component

Purpose

To investigate the effects of a trial femoral component on the intraoperative joint gap and intraoperative joint gap kinematics throughout the range of knee motion in minimally invasive surgery–total knee arthroplasty (MIS–TKA) with the gap technique.

Materials and methods

A total of 103 patients [15 men (15 knees) and 89 women (89 knees)] aged 50–88 years (mean 74.8 years) who received MIS–TKA with the gap technique were included. The intraoperative joint gap differences (90° flexion gap distance minus 0° extension gap distance) with and without the trial femoral component were compared. Subsequently, the intraoperative joint gap kinematics at 0°, 45°, 90°, and 120° with the trial femoral component were investigated.

Results

The intraoperative component gap difference (4.4 ± 2.7 mm) was larger than the estimated joint gap difference (1.2 ± 1.9 mm) (p < 0.01). The mean intraoperative component gap distances at 0°, 45°, 90°, and 120° of knee flexion were 14.7 ± 2.6, 19.0 ± 3.2, 19.2 ± 3.4, and 16.6 ± 3.3 mm, respectively. The intraoperative component gap distance increased significantly from 0° extension to 90° of knee flexion (p < 0.01), and then decreased significantly toward deep knee flexion at 120° (p < 0.01).

Conclusions

The trial femoral component influenced the intraoperative gap measurements, and increased the intraoperative gap difference. The joint gap kinematics with the trial femoral component were not constant throughout the range of knee motion, even if the appropriate joint gaps in extension and flexion were achieved. For acquisition of constant stability throughout the knee motion, the present results should be taken into account by surgeons performing MIS–TKA with the gap technique.     

Joint gap measurement in total knee arthroplasty using a tensor device with the same articulating surface as the prosthesis

Background

We developed a new tensor to measure the joint gap throughout knee flexion during total knee arthroplasty (TKA). This tensor has the same articular shape as that of the tibial liner, including the post structure and the curvature of femorotibial articular surface, to measure the gap intraoperatively under the same conditions as after TKA. The present study aimed to examine the precision of the new tensor for gap measurement after implantation.

Methods

We performed TKA using the modified gap technique in four cadaveric knees and measured the gaps using the new tensor. The intra-observer and inter-observer error of the tensor was analyzed using 168 measurements of the gaps as determined at least twice by two surgeons. In addition, the gaps in rotating-platform posterior-stabilized TKA were measured at seven positions with the knee bending from extension to full flexion.

Results

The inter-observer and intra-observer errors were 0.8 and 0.3 mm, respectively, indicating precise and reproducible gap measurement. The gaps before implantation in reduced patellar position were 12.1 mm at extension and 12.5 mm at 90° flexion. The gaps after implantation were 9.1, 12.9, 13.1, 13.5, 13.8, 13.3, and 10.1 mm at 0°, 30°, 45°, 60°, 90°, 120°, and full flexion, respectively.

Conclusions

The new tensor provides precise and reproducible measurements. Although the joint gap before implantation was parallel and equal at extension and 90° flexion, the joint gap after implantation was variable throughout knee flexion. This feature of the gap should be considered during the operation.     

Accuracy of soft tissue balancing in total knee arthroplasty

To the best of our knowledge, this is the first study to assess the accuracy of balancing of the flexion and extension gaps in total knee arthroplasty (TKA). Measurements of the heights of the flexion and extension gaps were obtained during 104 consecutive primary, posterior-stabilized TKAs in osteoarthritic patients. Clinically, all knees appeared to be well balanced intraoperatively. Rectangular flexion and extension gaps almost always were obtained within 1 mm (84%-89%). None of the knees was >3 mm from being perfectly rectangular. Equality of the flexion and extension gaps was more difficult to obtain (47%-57% were within 1 mm). With meticulous attention, perfect soft tissue balance is not always achieved in TKA.     

混合型单髁与全膝关节置换治疗膝内侧间室骨关节炎的疗效比较

目的：探讨Oxford第3代混合型单髁置换（unicompartmental knee arthroplasty,UKA）与全膝关节置换（total knee arthroplasty,TKA）治疗膝关节内侧间室骨关节炎的疗效。方法：回顾性分析2017年10月至2019年10月行膝关节置换术的156例患者,男44例,女112例,年龄50~75（58.76±4.97）岁。根据不同治疗方式分为单侧TKA组和单侧Oxford第3代混合型UKA组。单侧TKA 81例（81膝）,男23例,女58例,年龄51~75（58.60±5.01）岁;单侧Oxford第3代混合型UKA 75例（75膝）,男21例,女54例,年龄50~72（58.92±4.95）岁。比较两组临床评估指标,包括手术一般情况、相关并发症、美国膝关节协会评分（American Knee Society score,AKSS）临床评分和功能评分;影像评估指标包括髋膝踝角（hip-knee-ankle angle,HKA）、股骨假体内外翻角（femoral component valgus/varus angle,FCVA）、股骨假体后倾角（femoral component posterior slope angle,FCPSA）、胫骨假体内外翻角（tibial component valgus/varus angle,TCVA）、胫骨假体后倾角（tibial component posterior slope angle,TCPSA）,是否发生膝关节外侧间室进展、衬垫脱位、假体下沉、松动。结果：UKA组术中出血量、手术时间、住院天数均显著优于TKA组（P<0.05）,两组术后均未出现并发症。两组患者均获随访,时间24~54（38.01±8.90）个月。末次随访两组AKSS临床评分、功能评分、HKA均优于术前（P<0.05）。末次随访UKA组AKSS临床评分、功能评分均优于TKA组（P<0.05）,TKA组HKA优于UKA组（P<0.05）。末次随访两组TCVA、FCVA差异无统计学意义（P>0.05）,UKA组TCPSA、FCPSA大于TKA组（P<0.05）,UKA组未出现外侧室进展。结论：Oxford第3代混合型UKA治疗膝关节内侧间室骨关节炎,较TKA具有手术创伤小、失血量少、手术时间短、住院时间短、术后快速康复、膝关节功能恢复更好等优势,疗效满意。     

Influence of tibial slope on extension and flexion gaps in total knee arthroplasty: increasing the tibial slope affects both gaps

Purpose

Increasing the tibial slope is often performed if the flexion gap is narrower than the extension gap. The main hypothesis of this study is that increasing the tibial slope coincidentally enlarges the extension gap.

Methods

Twenty formalin-fixed cadaveric knees were obtained for study. After CT in full extension and 90° flexion, the data of each specimen were entered into a standardized coordinate system and virtual bone cuts were performed with incrementally increasing the posterior slope. Gaps were measured at tibiofemoral contact points in 90°-flexion and full extension in the medial and lateral compartment.

Results

Increasing the tibial slope did significantly widen both the extension and the flexion gaps (p?p?Conclusions Increasing the tibial slope beyond the pre-operative planning in order to widen a tight flexion gap intra-operatively is not recommended as doing so will increase the extension gap simultaneously and will make the medial and lateral flexion gaps unequal.     

Varus Gonarthrosis Predisposes to Varus Malalignment in TKA

Postoperative alignment is a predictor for long-term survival of total knee arthroplasty (TKA). The purpose of this study was to evaluate whether or not preoperative deformities predispose to intraoperative malposition of TKA components. A retrospective radiographic analysis of 53 primary TKA cases was performed. Preoperative AP hip to ankle and lateral knee radiographs were compared with postoperative views to evaluate component positioning. The following angles were measured: the hip–knee–ankle (HKA) angle expressing the mechanical axis of the leg, the mechanical lateral distal femur angle (mLDFA), the medial proximal tibia angle (MPTA), the posterior distal femur angle (PDFA), and the posterior proximal tibia angle (PPTA). Postoperative measurement of the HKA revealed 34.0% of the cases had a deviation of >±3° from neutral alignment. Sixteen knees (30.2%) were in varus and, with one exception, all presented with severe varus gonarthrosis prior to surgery with a mean tibiofemoral angle of 12.4° compared with 1.0° of valgus in the optimally aligned group. Patients (93.3%) with preoperative valgus malalignment showed optimal postoperative HKA. Odds ratios for malalignment of TKA for varus knees in comparison with valgus knees were 7.1 for HKA, 2.4 for MPTA, 4.9 for PDFA, and 1.7 for PPTA. The overall number of outliers in the presented data corresponds well with reports from other authors using different implants and guide systems. The presented data indicate that patients with preoperative varus alignment have a higher risk of postoperative implant malposition than patients with valgus alignment. The data supports that preoperative varus deformity predisposes to varus malposition of TKA. The risk for intraoperative malposition is significantly lower in valgus knees.     

全膝关节置换术后股胫关节运动学轨迹的数字化模型研究

 目的 通过透视技术结合数字化模型注册技术分析全膝关节置换术后股骨假体与胫骨垫片之间的相对运动和接触位置。方法 2007年7月至2008年6月,接受GENESISⅡ假体全膝关节置换术患者16例,均为女性;年龄56～76岁,平均66.4岁。随访48～60个月,平均(56±3)个月。采用膝关节学会评分(Knee Society Score,KSS)评价膝关节功能;采用循环透视方法获取影像学数据,对假体逆向数字建模,进行数字模型和影像学数据的匹配,重建膝关节的三维运动;测量股骨内、外髁接触位置的移动,计算胫骨内旋角度,测量股骨凸轮和胫骨立柱的接触时相和范围。结果 末次随访时KSS膝评分(93±5)分,功能评分(88±13)分,与术前比较差异有统计学意义。股骨内髁的移动范围(8.5±2.5) mm,外髁的移动范围(9.5±4.8) mm,胫骨内旋角度2.5°±8.4°。屈膝约30°～40°时凸轮和立柱发生接触,立柱后方的接触范围(8.0±1.8) mm。胫骨平台后倾角度越大,凸轮和立柱的接触越晚。结论 全膝关节置换术后股胫关节的运动学特征与正常膝关节不同,膝关节屈曲10°~30°时股骨内髁前移,屈曲大于40°后股骨内、外髁后移,胫骨平台后倾与凸轮和立柱的接触时相有相关性。     

A lateral fracture step-off of 2mm increases intra-articular pressure following tibial plateau fracture

IntroductionThe aim of this study was to evaluate the effects of increasing posttraumatic step-offs after lateral tibial plateau fracture reduction on the intra-articular pressure.Materials and MethodsIn eight fresh-frozen human cadaveric knees with intact menisci, a standardized sagittal osteotomy of the lateral tibial condyle was performed as an OTA/AO type 41-B1 fracture-model. The fragment was fixed by a customized sled including an angular stable tibia plate to evaluate step-offs from 0 mm to 8 mm in 1mm increments. In a servo-hydraulic testing machine, an axial force was applied to the tibial plateau in 0° (700N), 15° (700N), 30° (700N), 60° (350N), and 90 ° (350N) of flexion while the joint pressure was recorded by two pressure sensors.ResultsA 1mm step-off did not result in an increased joint pressure. At 60° of flexion a 2mm step-off increased the lateral joint pressure by 61.84kPa (P = 0.0027). In 30° of flexion, a 3mm step raised the lateral joint pressure by 66.80kPa (p = 0.0017), whereas in 0°, 15° and 90° of flexion, a 4mm step increased the pressure by >50kPa (P < 0.05). Concomitant medial joint pressure increments were lower than those in the lateral plateau. A significant increase of 19-24kPa in the medial joint pressure was detected in 90° of flexion with a 1mm lateral step (P = 0.0075), in 15° and 60° of flexion with a 2mm step (P < 0.05), in 0° of flexion with a 4mm step (P = 0.0215) and in 30° of flexion with a 7mm step (P = 0.0487).ConclusionLateral fracture step-offs of 2mm or larger should be reduced intraoperatively to avoid large increases in lateral joint pressure.     

Influence of hip position on knee flexion angle in patients undergoing total knee arthroplasty

The influence of hip position on knee flexion angle before total knee arthroplasty (TKA) and that after TKA were investigated and compared. Sixty-six patients (70 knees) with osteoarthritis who were undergoing TKA were examined using lateral radiographs of maximum knee flexion angle with the hip joint at 0 degrees extension and 90 degrees flexion. The postoperative rate of decrease in knee flexion angle caused by hip extension was significantly larger compared with the value before surgery. The preoperative rate of decrease in knee flexion angle caused by hip extension showed strong inverse correlation with the preoperative and postoperative knee flexion angle ratio. In conclusion, tightness of the extensor mechanism is present in all knees undergoing TKA and especially has a strong influence on the postoperative flexion angle of the knee.     

Good Postoperative Flexion Angle Improves Knee Function and Improvement of Flexion Angle Increases Patient Satisfaction After Total Knee Arthroplasty

BackgroundTotal knee arthroplasty (TKA) is a well-established procedure for treating knee joint diseases. However, the postoperative range of motion (ROM) varies and is an important indicator of TKA success. Recently, patient-reported outcome measures (PROMs) and patient satisfaction have drawn attention. However, the relationship between ROM and knee function obtained by PROM and satisfaction is not well understood.MethodsWe retrospectively reviewed the data of 375 patients who underwent 500 primary TKA procedures. We measured the ROM before and after surgery. Knee joint function was evaluated using the Knee Injury Osteoarthritis Outcome Score, a PROM, and patients were classified into good function and poor function groups. Patient satisfaction was evaluated on a 5-graded scale as overall satisfaction, and patients were divided into a satisfied or a dissatisfied group according to the obtained scores. ROM was compared between the 2 groups, then significantly different factors were analyzed using multiple logistic regression analysis. Moreover, cut-off points of ROM for obtaining good function and patient satisfaction were determined using ROC curve analysis.ResultsThe postoperative flexion angle had a significant effect on knee function (P < .001). The cut-off value of the postoperative flexion angle for good knee function was 120°. The improvement in flexion angle had a significant effect on patient satisfaction (P = .004). The cut-off value for the improvement in the flexion angle was 5°.ConclusionThe postoperative flexion angle had a significant effect on knee function and improvement in the flexion angle had a significant effect on patient satisfaction.