髌股关节发育不良对髌骨脱位磁共振成像表现的影响

背景：当存在髌股关节发育不良时,髌骨脱位的损伤程度较轻,因此更加依赖影像学诊断。 目的：比较髌股关节发育不良患者和髌股关节发育正常患者髌骨脱位时磁共振成像（MRI）表现的异同。 方法：回顾性分析54例经临床证实的髌骨脱位患者的MRI影像学资料。髌股关节发育不良患者32例,髌股关节发育正常患者22例。记录患者MRI中髌骨内侧骨挫伤或撕脱骨折、髌骨关节面骨软骨骨折、股骨外侧髁外侧部骨挫伤、髌股内侧支持带撕裂等情况。 结果：髌股关节发育不良组的32例患者中,髌骨内缘骨折12例,内侧支持带损伤10例,髌骨软骨损伤7例,股骨外髁骨挫伤18例;髌股关节发育正常组的22例患者中,髌骨内缘骨折8例,内侧支持带损伤14例,髌骨软骨损伤14例,股骨外髁骨挫伤14例。两组在内侧支持带损伤和髌骨内缘骨折上有显著统计学差异（P＜0.05）。 结论：MRI可以较好地诊断髌骨脱位。当髌股关节发育不良时,内侧支持带损伤和髌骨内缘骨折的发生率降低。     

Comparison of patellar mobility in female adults with and without patellofemoral pain

STUDY DESIGN: Case control study. OBJECTIVE: To compare the patellar mobility of female adult subjects with and without patellofemoral pain (PFP). BACKGROUND: Although abnormal patellar mobility is believed to be one of the causes of PFP, there is currently no published evidence to support this contention. In part, this lack of evidence is because a reliable clinical measurement method to measure patellar mobility and objective criteria to define abnormal patellar mobility have not been established. METHODS AND MEASURES: The study sample was comprised of 22 females with PFP (PFP group) and 22 females who had no knee pain (control group), matched by age, height, and body mass index to the subjects with PFP. Patellar mobility was measured objectively using a specially designed apparatus. Measurements of lateral and medial patellar displacement, patellar mobility balance (lateral minus medial patellar displacement), lateral patellar mobility index (lateral patellar displacement divided by patellar width), and medial patellar mobility index (medial patellar displacement divided by patellar width) were used. RESULTS: Lateral and medial patellar mobility values were not significantly different between the individuals in the PFP and control groups. When normal patellar mobility was arbitrarily defined as the average mobility +/- 2 SDs, based on the data from the control group, normal lateral patellar displacement was within a range of 7.2 to 17.6 mm and normal medial patellar displacement was within a range of 6.8 to 14.0 mm. The intraclass correlation coefficient for intratester and intertester reliability of lateral and medial patellar displacement measurements varied from 0.80 to 0.97. CONCLUSION: Although there were no significant differences in patellar mobility between females with and without PFP, these measurements give reference information about normal patellar mobility for this group. LEVEL OF EVIDENCE: Diagnosis, level 5.     

The effect of patellar button placement and femoral component design on patellar tracking in total knee arthroplasty.

The effects of patellar button position and femoral component design on patellar tracking were investigated roentgenographically and arthroscopically using fresh-frozen adult anatomic specimen knees. Patellar tracking was evaluated for medial/lateral position and tilting angle deviation by comparing preoperative normal values to total knee replacement performance with the following variables: (1) femoral component design; symmetrical total condylar type with a 3-mm central patellar groove and a component with a 3-mm raised lateral patellar flange and 1-mm deepened patellar groove; and (2) patellar button placement; central insertion; and 10-mm medialized insertion. In the roentgenographic study, medialized position of the patellar button allowed the bony portion of the patella to assume its normal lateral position and tilt throughout the knee range of motion. A combination of medialized position of the patellar button and deepening of the patellar groove provided the most anatomically correct position and the most normal tilting of the bony structure of the patella. In the arthroscopic study, the centralized patellar position caused significant lateral tracking and subluxation relative to the femoral component, whereas the medialized position eliminated this tracking disorder. Deepening the patellar groove minimized the intraarticular tracking abnormality and constrained the patellar button in the patellar groove. These results show that the position of the patellar button and femoral component design exert a major influence on patellar tracking.     

Patellar contact forces with and without patellar resurfacing in total knee arthroplasty.

Patellar contact forces were measured in 7 fresh-frozen cadaver knees during continuous flexion-extension cycling for the normal knee and after total knee arthroplasty without and with patellar resurfacing using 2 prosthesis systems with different designs for the femoral and patellar components. Analysis of variance with specimen as a repeated measure was used to examine the effect of contact surface. When compared to normal knees, total knee arthroplasty without patellar resurfacing resulted in no change in patellar contact forces. The magnitude of the inferosuperior patellar shear force increased significantly after patellar replacement with an oval, biconcave patellar component and increased further after replacement with an oval, domed patellar component. There were no significant changes in the mediolateral and anteroposterior contact force components after patellar replacement.     

Factors affecting patellar tracking after total knee arthroplasty

This study examined factors that influence patellar tracking after total knee arthroplasty. A total of 62 knees were evaluated radiographically for postoperative patellar tracking. Six factors were examined regarding their influence on postoperative patellar tracking. This study showed the effects of patellar component position, patellar resection angle, and lateral retinacular release on postoperative patellar tracking. There was no significant effect of the remaining 3 factors: the thickness of the patellar resection, preoperative patellar tilt, and rotational alignment of the femoral component. A medialized patellar component and obliquity of resection of the patella are effective for obtaining proper patellar tracking, whereas the evaluation of the influence of the external rotation of the femoral component requires more clinical studies.     

Effect of patellar meniscus on patellofemoral contact stress in total knee arthroplasty

The effect of a meniscus of fibrous tissue (patellar meniscus), on patellofemoral contact area and stresses was evaluated. Two knees with total knee arthroplasty and dome-shaped patellar components were retrieved at autopsy. Both had substantial fibrous menisci surrounding the dome of the patellar component. Contact area and contact stresses were measured with a digital electronic sensor, first with the patellar meniscus intact, then again after the patellar meniscus was removed. No dramatic difference was detected in patellofemoral contact area and contact stresses between the patellas with an intact or removed patellar meniscus, and there was no detectable load under the patellar meniscus. The results of this case study suggest that fibrous tissue surrounding the dome-shaped patellar component does not share compressive loads with the patellar component.     

Reliability and validity of a new caliper for measuring patellar thickness

The process of patellar resurfacing during total knee arthroplasty involves measuring patellar thickness. The optimal residual patellar bone thickness has been questioned. The surgeon's ability to measure patellar thickness currently rests on a standard caliper. Standard methods involve use of a smooth-mouthed caliper, which can overestimate patellar thickness because of soft tissue interposition. This brief communication introduces a new spiked caliper design that can be used to measure patellar bone thickness more accurately. Improved accuracy in measuring patellar bone thickness allows the operating surgeon to assess more correctly a patient's patellar bony status. This knowledge may result in fewer postoperative fracture complications resulting from deficiencies of bone owing to excessive resection.     

Distal femoral extension osteotomy and patellar tendon advancement or shortening in ambulatory children with cerebral palsy: A modified Delphi consensus study and literature review

Purpose:In children with cerebral palsy, flexion deformities of the knee can be treated with a distal femoral extension osteotomy combined with either patellar tendon advancement or patellar tendon shortening. The purpose of this study was to establish a consensus through expert orthopedic opinion, using a modified Delphi process to describe the surgical indications for distal femoral extension osteotomy and patellar tendon advancement/patellar tendon shortening. A literature review was also conducted to summarize the recent literature on distal femoral extension osteotomy and patellar tendon shortening/patellar tendon advancement.Method:A group of 16 pediatric orthopedic surgeons, with more than 10 years of experience in the surgical management of children with cerebral palsy, was established. The group used a 5-level Likert-type scale to record agreement or disagreement with statements regarding distal femoral extension osteotomy and patellar tendon advancement/patellar tendon shortening. Consensus for the surgical indications for distal femoral extension osteotomy and patellar tendon advancement/patellar tendon shortening was achieved through a modified Delphi process. The literature review, summarized studies of clinical outcomes of distal femoral extension osteotomy/patellar tendon shortening/patellar tendon advancement, published between 2008 and 2022.Results:There was a high level of agreement with consensus for 31 out of 44 (70%) statements on distal femoral extension osteotomy. Agreement was lower for patellar tendon advancement/patellar tendon shortening with consensus reached for 8 of 21 (38%) of statements. The literature review included 25 studies which revealed variation in operative technique for distal femoral extension osteotomy, patellar tendon advancement, and patellar tendon shortening. Distal femoral extension osteotomy and patellar tendon advancement/patellar tendon shortening were generally effective in correcting knee flexion deformities and extensor lag, but there was marked variation in outcomes and complication rates.Conclusion:The results from this study will provide guidelines for surgeons who care for children with cerebral palsy and point to unresolved questions for further research.Level of evidence:level V.     

Patellar component positioning in total knee arthroplasty

Five human anatomic specimen knees were used to determine the effect of patellar component position on patellofemoral kinematics, contact pressures, and contact areas after total knee arthroplasty using a polyethylene, domed patellar component. Each patellar component was positioned at the anatomic center of the resected patellar surface and then repositioned 5 mm proximally, distally, medially, and laterally. Patellar tilt was greatest with medial positioning of the patellar component and least with central and lateral positioning. At higher knee flexion angles, patellofemoral joint contact pressures increased at the medial facet with the medialized component and at the lateral facet for the lateralized component. The centralized component had the most evenly balanced patellar facet contact pressures. Distally positioned patellar components resulted in decreased patellar component loading at higher knee flexion angles. Central positioning of the patellar component results in optimal patellofemoral mechanics when maximal coverage of the resected patella is desired.     

Patellar prosthesis positioning in total knee arthroplasty. A roentgenographic study

Patellar prosthesis positioning in 40 primary total knee replacements was evaluated with regard to (1) patellar tilt, (2) angle between the patellar component and patellar bony remnant, (3) lateral versus medial placement, (4) patellar height, and (5) size of the patellar component versus patellar length. Two different designs were evaluated. Twenty knees that were resurfaced with a patellar button prosthesis and implanted with conventional surgical technique constituted Group A. Twenty knees that were resurfaced with a new biconvex prosthesis and implanted with specially designed instrumentation constituted Group B. For Group A, the patellar tilt averaged 4.25 degrees preoperative and 8.35 degrees postoperative. For Group B the patellar tilt averaged 4.60 degrees preoperative and 1.83 degrees postoperative. In Group B, there was significant improvement in patellar position, with only two patients showing values exceeding the neutral range (p = 0.0409). The angle between the patellar component and the bony remnant in Group A averaged 5.975 degrees, and in Group B, 1.447 degrees. Two patients in Group A and 18 patients in Group B had values in the normal range for patellar tilt and the angle between the prosthesis and the bone. The prosthesis was inserted medial to the patellar center in six patients in Group A and one patient in Group B. A significant decrease in patellar height was noted for both groups, but values were still within the normal range. Both groups showed significant increase in the postoperative articular length, indicating that oversized prostheses were inserted and excess bone removed.     

Model predictions of increased knee joint loading in regions of thinner articular cartilage after patellar tendon adhesion

Patellar tendon adhesion is a complication from anterior cruciate ligament (ACL) reconstruction that may affect patellofemoral and tibiofemoral biomechanics. A computational model was used to investigate the changes in knee joint mechanics due to patellar tendon adhesion under normal physiological loading during gait. The calculations showed that patellar tendon adhesion up to the level of the anterior tibial plateau led to patellar infera, increased patellar flexion, and increased anterior tibial translation. These kinematic changes were associated with increased patellar contact force, a distal shift in peak patellar contact pressure, a posterior shift in peak tibial contact pressure, and increased peak tangential contact sliding distance over one gait cycle (i.e., contact slip). Postadhesion, patellar and tibial contact locations corresponded to regions of thinner cartilage. The predicted distal shift in patellar contact was in contrast to other patellar infera studies. Average patellar and tibial cartilage pressure did not change significantly following patellar tendon adhesion; however, peak medial tibial pressure increased. These results suggest that changes in peak tibial cartilage pressure, contact slip, and the migration of contact to regions of thinner cartilage are associated with patellar tendon adhesion and may be responsible for initiating patellofemoral pain and knee joint structural damage observed following ACL reconstruction. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29: 1168–1177, 2011     

The need for patellar resurfacing in total knee arthroplasty: a literature review

The controversy over whether or not to routinely resurface the patella during a total knee arthroplasty has persisted despite three decades of successful joint replacement procedures. Advocates for routine patellar resurfacing admit the occasional need for secondary patellar resurfacing and declare increased incidence of anterior knee pain in patients with non‐resurfaced patellae as a cause for worry. Surgeons that leave the patella unresurfaced cite avoidance of complications that include patellar fracture, avascular necrosis, patellar tendon injury and instability. This review discusses the available literature on patellar resurfacing through an evidence‐based analysis of randomized and pseudo‐randomized controlled trials and published meta‐analyses to date. The published literature seems to favour resurfacing the patellar routinely. Selective patellar resurfacing would be the ideal solution if sound pre‐operative criteria could be established. So far, a method for accurately predicting which patients can avoid patellar resurfacing has not been found. Future research looking at patellar resurfacing should concentrate on developing criteria for selecting those patients that would benefit from patellar resurfacing and those that would do as well without resurfacing, and thus, limiting potential surgical complications.     

传统与改良Elmslie-Trillat术治疗髌骨不稳定的生物力学比较

目的 评价传统与改良Elmslie-Trillat术治疗髌骨不稳定的生物力学特性,为改良Elmslie-Trillat术治疗髌骨不稳定提供生物力学依据.方法 先对12具新鲜冰冻成人尸体膝关节完整标本(完整膝关节组,12具)进行生物力学测试测量髌骨移位距离,切断内侧髌股韧带制成髌骨不稳定模型(髌骨不稳定模型组,12具)后再测量髌骨移位距离,然后随机再分为2组(传统Elmslie-Trillat术组及改良Elmslie-Trillat术组,每组6具标本)分别采用传统和改良Elmslie-Trillat术矫正.膝关节屈曲30°位固定胫骨及股骨端,将标本安装在MTS-858实验机上,通过髌骨中心外侧施加20 N的载荷,测量髌骨移位距离.结果 完整膝关节组、髌骨不稳定模型组、传统Elmslie-Trillat术组及改良Elmslie-Trillat术组的髌骨外侧移位距离平均分别为(6.2±0.6)、(11.3±0.9)、(6.4±0.8)、(6.7±0.8)mm,4组外侧减内侧移位距离平均分别为(-1.5±0.5)、(3.5±0.4)、(-1.4±1.0)、(-1.3±1.0)mm.髌骨不稳定模型组的外侧移位距离和外侧减内侧移位距离分别与其他3组比较,差异均有统计学意义(P＜0.05);完整膝关节组、传统Elmslie-Trillat术组及改良Elmslie-Trillat术组的外侧移位距离和外侧减内侧移位距离比较差异均无统计学意义(P＞0.05).结论 内侧髌股韧带是髌骨的主要稳定因素.与传统Elmslie-Trillat术比较,改良Elmslie-Trillat术同样能改善髌骨异常力线,减少相同应力下的髌骨位移.

Abstract：

Objective To evaluate the biomechanical performance of the modified Elmslie-Trillat procedure in the treatment of patellar instability as compared with traditional Elmslie-Trillat procedure.Methods Twelve fresh frozen cadaveric specimens of intact knee joint were used in this study.First biomechanical measurements were performed to compare the patellar displacements between the intact knee joints and models of patellar instability which were made by cutting the medial patellofemoral ligaments.Next the models of patellar instability were randomized into 2 groups for treatments with traditional and modified Elmslie-Trillat procedures respectively.After the tibiofemoral joint was held at 30 degrees of flexion, a load of 20 N was applied to the lateral center of the patella.The patellar displacements were measured with transducers in an Instron Testing System.Results The lateral patellar displacement was respectively 6.2 ±0.6 mm, 11.3 ± 0.9 mm, 6.4 ± 0.8 mm and 6.7 ± 0.8 mm and the lateral minus medial patellar displacement was respectively - 1.5 ± 0.5 mm, 3.5 ± 0.4 mm, - 1.4 ± 1.0 mm and - 1.3 ± 1.0 mm for the 4 groups of intact knee joint, patellar instability, traditional Elmslie-Trillat procedure treatment and modified Elmslie-Trillat procedure treatment.There were significant differences in both of the patellar displacements between the patellar instability group and the other 3 groups ( P ＜ 0.05).There was no significant difference in both of the patellar displacements among the 3 groups of intact knee joint, traditional Elmslie-Trillat procedure treatment and modified Elmslie-Trillat procedure treatment ( P ＞ 0.05 ).Conclusion Since the medial patellofemoral ligament is a main stable factor for patella, patellar abnormal traction can be improved and patellar displacement can be reduced under the same loading by both modified and traditional Elmslie-Trillat procedures.     

Patellar component resection arthroplasty for the severely compromised patella

When severe bone loss precludes reimplantation of a new patellar component during revision knee arthroplasty, the treatment options include patellar bone grafting, patellar component resection arthroplasty, and patellectomy. The purpose of this study was to evaluate the clinical and functional results of patellar component resection arthroplasty for the severely compromised patella for which insertion of another patellar component was not possible. Thirty-five knees (31 patients) were treated with patellar component resection arthroplasty for aseptic patellar component failure associated with severely compromised patellar bone stock. Followup averaged 7.9 years (range, 2-18 years). There was a significant improvement in Knee Society pain and function scores. Pain relief was more dramatic than functional improvement. The range of motion also improved significantly and in particular preoperative extensor lag was resolved in the majority of patients. Patients treated with isolated patellar resection arthroplasty were more likely to have continuing pain and require reoperation compared with patients who had concomitant revision of the tibial and femoral components. Correct positioning and the stability of tibial and femoral components should be tested carefully at the time of patellar resection arthroplasty and considered for revision if malpositioned either axially or rotationally.     

The effect of component placement on knee kinetics after arthroplasty with an unconstrained prosthesis.

The mechanical success of a total knee replacement demands stable patellar tracking without subluxation and, stable tracking, in turn, can depend largely on the medial-lateral forces restraining the patella. Patellar button medialization has been advocated as a means of reducing subluxation, and experimental evidence has shown femoral component rotation also affects medial-lateral forces. Surgeons have choices in femoral component rotation and patellar button medialization and must frequently make intra-operative decisions concerning component placement because of anatomical variations among patients. Thus, in seeking to minimize medial-lateral patellar force, we examined the effects of patellar button medialization and external femoral component rotation. The study used an unconstrained total knee system implanted in nine cadaveric specimens tested on a knee simulator operating through flexion angles up to 100 degrees. Tests included all combinations of external femoral component rotation of 0 degree, 2.5 degrees, and 5 degrees and patellar placement at the geometric center and at 3.75 mm medial to the geometric center. A video-based motion analysis system tracked patellar and tibial kinematics while a six-component load cell measured patellofemoral loads. Repeated measures analysis of variance revealed a statistically significant decrease in the average medial-lateral force with button medialization but no significant change with femoral component rotation. Neither femoral component rotation nor patellar button medialization had an effect on the normal component of the patellar reaction force. External femoral component rotation did cause significant increases in lateral patellar tilt, in tibial varus angle, and in external tibial rotation. Button medialization caused significant increases in lateral patellar tracking, lateral patellar tilt and external tibial rotation. The results in medial-lateral patellar forces quantify the benefit of patellar button medialization and discount any benefit of femoral rotation. The change in tibial kinematics with patellar button medialization and femoral component rotation cannot be measured in vivo with current technology, and the precise clinical implications are unknown.     

Dislocated patella associated with below-knee amputation in adolescent patients

One-third of the adolescent patients followed up in our prosthetic clinic have developed patellar dislocation. Four cases are described, and radiographs are evaluated for femoral-tibial alignment, patellar height, and tibial length. Patella alta was present in each patient. We propose that the forces associated with the patellar tendon-bearing prosthesis may produce elongation of the patellar tendon in young patients and predispose them to patellar instability.     

Familial association of femoral trochlear dysplasia with recurrent bilateral patellar dislocation

Femoral trochlear dysplasia is an anatomic deformity that predisposes patients to patellar instability, including patellar subluxation and dislocation, and can lead to severe patellofemoral joint degeneration if left untreated. Femoral trochlear dysplasia leading to recurrent bilateral patellar dislocation has rarely been reported as having a familial association. Orthopedic surgeons who encounter patients presenting with chronic patellar instability with no underlying disease or syndrome should be aware of the presence of femoral trochlear dysplasia leading to recurrent bilateral patellar dislocation. Although femoral trochlear dysplasia remains uncommon, the presence of bilateral recurrent patellar dislocation in multiple members of the same family is highly suggestive of genetic inheritance.This article describes 3 patients from 1 family who presented with femoral trochlear dysplasia leading to recurrent bilateral patellar dislocation. To our knowledge, this is the second article to describe a familial form of femoral trochlear dysplasia associated with recurrent bilateral patellar dislocation and is the first article in English. A lower threshold for screening and early intervention for symptomatic family members may be indicated to prevent the long-term effects of chronic patellar subluxation, dislocation, and patellofemoral arthritis.     

Primary bone grafting following graft procurement for anterior cruciate ligament insufficiency

A technical recommendation of primarily bone grafting the patellar tendon graft site created following harvesting the central third of the free bone-tendon-bone patellar tendon graft for anterior cruciate ligament (ACL) insufficiency is presented. Harvesting a patellar bone-tendon-bone graft produces a stress riser that increases the potential risk of a patellar fracture. Primary bone grafting of the patellar region is recommended as a simple and safe solution, especially if a graft wider than 10-12 mm or deeper than 6 mm is taken. We feel that this will reduce even further the small likelihood of late patellar fracture. Using these principles, we have not had any late patellar fractures in over 135 consecutive ACL reconstructions since July, 1986.     

Comparison between patellar resurfacing with an inset plastic button and patelloplasty

Of 101 patients who underwent knee replacement with the Tricon P prosthesis and were followed up for 2 or more years, 68 had patellar resurfacing with a recessed press-fit plastic button and 43 patients had patelloplasty (shaving of the patella and removal of osteophytes). All patients were followed up for more than 2 years. Three percent of the patients who had patellar resurfacing, later had patellar fractures; 4.6% of the patients who had patelloplasty initially, subsequently required patellar replacement. There were no instances of loosening of the patellar replacement. Patellofemoral aching was experienced by 7.6% of the patients who had patellar resurfacing and by 17.6% of those who did not. Of the patients who had patellar resurfacing, 61.5% could climb stairs without aids using the replaced side as the lead leg compared with 37.2% of the patients who had patelloplasty. Overall ratings of the surgical results were similar for the two groups. The author concludes that patellar resurfacing improves the quality of the result and that there are few drawbacks to the use of an inset patellar button.     

Failure of the all-polyethylene patellar component after total knee arthroplasty

From 1991 to 1996, 953 cases of porous-coated anatomic modular knee prostheses with all-polyethylene patellar components were implanted. Among them, 4 cases had breakage of the patellar component at the peg-button interfaces. One had loosening of the patellar component by cutting out the patellar bony bed. Heavy body weight, weakness of the pegs of the all-polyethylene patellar component, and osteonecrosis of the patella were conceived as the causes of failure.