The sulcus angle and malalignment of the extensor mechanism of the knee

Anterior knee pain due to dysplasia of the extensor mechanism is common. We have studied 137 knees (103 patients) in order to identify a rapid and reproducible radiological feature which would indicate the need for further analysis. Overall, 67 knees (49%) had at least one radiological abnormality; 70 (51%) were considered normal. There were five cases of Dejour type-3 dysplasia of the femoral trochlea, nine of type-2 and 12 of type-1. There were 49 cases of patella alta and five of patella infera. Four knees had an abnormal lateral patellofemoral angle (patellar tilt), and in 15 knees there was more than one abnormality. Classification of trochlear dysplasia was difficult and showed poor reproducibility. This was also true for the measurement of the lateral patellofemoral angle. Patellar height was more easily measured but took time. The sulcus angle is an easily and rapidly measurable feature which was reproducible and was closely related to other features of dysplasia of the extensor mechanism. The finding of a normal sulcus angle suggested that seeking other radiological evidence of malalignment of the extensor mechanism was unlikely to reveal additional useful information. The severity of other features of dysplasia of the extensor mechanism correlated with increasing sulcus angle.     

Radiographic evaluation of patellofemoral alignment in kinematically aligned total knee arthroplasty: A comparative study with mechanically aligned total knee arthroplasty

BackgroundKinematically aligned total knee arthroplasty (KA-TKA), in which femoral component is placed 3–5° of internal rotation relative to mechanically aligned (MA)-TKA, may have a potential risk of patellofemoral malalignment. This study aimed to assess patellofemoral alignment and compare the data between KA-TKA and MA-TKA, and the relationship with patellofemoral radiographic parameters and patient reported outcomes.MethodsAmong patients who underwent TKA in 2015 and 2016 in our institute, 28 KA-TKAs with a metal-backed patellar component were retrospectively assessed for patellofemoral alignment, and 28 MA-TKAs with a metal-backed patellar component served as controls. A year postoperatively, patellar tilt and shift at 30°, 60°, and 90° knee flexion were measured on Merchant views and compared between the two TKAs. Implant positioning in each patient was assessed based on preoperative CT images and correlations of femoral component positioning with patellar tilt/shift were assessed.ResultsPatellar shift at 30° flexion was significantly greater in KA-TKA than in MA-TKA (p = 0.04), whereas patellar tilt angle was comparable between the two TKAs. No statistical correlation was evident between femoral component positioning and patellar shift/tilt, regardless of knee flexion angle in the two TKAs. Knee Society Score 2011 at 1 year follow-up was comparable in all subcategories between the two TKAs.ConclusionRadiographic analysis of KA-TKA revealed lateral shift of the patella at 30° knee flexion at 1 year postoperatively, however patients with patellar shift were asymptomatic. Further long-term observation is required to examine the impact of KA-TKA on the patellofemoral complication.     

Effect of femoral and tibial component position on patellar tracking following total knee arthroplasty: 10-year follow-up of Miller-Galante I knees

Rotational alignment of the femoral and tibial components using computed tomography (CT) was evaluated to establish if errors of alignment have a significant effect on patellofemoral complications. From 1987-1990, 54 knees in 39 patients were replaced with the Miller-Galante I knee system. Of these, 10 patients (13 knees) comprised this study. All patients had osteoarthritis. Mean patient age at surgery was 70.3 years. Mean follow-up was 10.3 years. On CT, rotational position of the femoral component relative to the epicondylar axis and the position of the tibial component relative to the tibial tubercle were evaluated. Patellar displacement and patellar tilt angle also were evaluated when the knee was flexed at 30 degrees. Mean rotation of the femoral component was 6.1 degrees of internal rotation (2.7 degrees-11.2 degrees). Mean rotation of the tibial component was 16.7 degrees of internal rotation (2.4 degrees-27.7 degrees). Mean lateral patellar tilt angle was 2.9 degrees (-6.0 degrees-11.9 degrees), and mean lateral displacement was 2.7 mm (-3.2-8.9 mm). Rotational position of both the femoral and tibial components showed a statistically significant correlation with the patellar tilt angle. This study showed the internally rotated femoral and tibial component were related to the patellar maltracking. This malalignment of the components, as well as nonanatomical patellar groove and metal-backed patellar component, could be one of the causes of the patellofemoral complications with the Miller-Galante I knee.     

The influence of iliotibial tract on patellar tracking

Thirty patients with 49 snapping hips and patellar malalignment underwent surgical release of the iliotibial tract contracture over the trochanteric area. Minimal follow-up was 2 years (average 4.6 years, range: 2-9 years). Eight patients underwent computed tomography (CT) preoperatively and 1 month postoperatively to investigate the patellar location in the patellofemoral articulation with knee bending at 0 degrees, 20 degrees, 45 degrees, 60 degrees, and 90 degrees. Significant improvements in the congruence angle and lateral patellofemoral angle were noted on Merchant radiograph for all knees (P<.01). On CT, at 20 degrees and 45 degrees knee bending, all congruence, lateral patellofemoral, and patellar tilt angles significantly improved postoperatively in 8 knees (P<.01). Iliotibial tract affects patellar tracking and dominates lateral patellar supporting structures.     

Patella alta: association with patellofemoral alignment and changes in contact area during weight-bearing

BACKGROUND: Patella alta is a condition which may predispose individuals to patellofemoral joint dysfunction. We compared patellofemoral joint alignment and contact area in subjects who had patella alta with subjects who had normal patellar position, to determine the effect of high vertical patellar positions on knee extensor mechanics. METHODS: Twelve subjects with patella alta and thirteen control subjects participated in the study. Lateral patellar displacement (subluxation), lateral tilt, and patellofemoral joint contact area were quantified from axial magnetic resonance images of the patellofemoral joint acquired at 0 degrees , 20 degrees , 40 degrees , and 60 degrees of knee flexion with the quadriceps contracted. RESULTS: With the knee at 0 degrees of flexion, the subjects with patella alta demonstrated significant differences compared with the control group, with greater lateral displacement (mean [and standard error], 85.4% +/- 3.6% and 71.3% +/- 3.0%, respectively, of patellar width lateral to the deepest point in the trochlear groove; p = 0.007), greater lateral tilt (mean, 21.6 degrees +/- 1.9 degrees and 15.5 degrees +/- 1.8 degrees ; p = 0.028), and less contact area (157.6 +/- 13.7 mm(2) and 198.8 +/- 14.3 mm(2); p = 0.040). Differences in displacement and tilt were not observed at greater knee flexion angles; however, contact area differences were observed at all angles evaluated. When data from both groups were combined, the vertical position of the patella was positively associated with lateral displacement and lateral tilt at 0 degrees of flexion and was negatively associated with contact area at all knee flexion angles. CONCLUSIONS: These data indicate that the vertical position of the patella is an important structural variable that is associated with patellofemoral malalignment and reduced contact area in patients with patella alta.     

Patellofemoral joint kinematics in individuals with and without patellofemoral pain syndrome

BACKGROUND: Patellofemoral pain syndrome is a prevalent condition in young people. While it is widely believed that abnormal patellar tracking plays a role in the development of patellofemoral pain syndrome, this link has not been established. The purpose of this cross-sectional case-control study was to test the hypothesis that patterns of patellar spin, tilt, and lateral translation make it possible to distinguish individuals with patellofemoral pain syndrome and clinical evidence of patellar malalignment from those with patellofemoral pain syndrome and no clinical evidence of malalignment and from individuals with no knee problems. METHODS: Three-dimensional patellofemoral joint kinematics in one knee of each of sixty volunteers (twenty in each group described above) were assessed with use of a new, validated magnetic resonance imaging-based method. Static low-resolution scans of the loaded knee were acquired at five different angles of knee flexion (ranging between -4 degrees and 60 degrees). High-resolution geometric models of the patella, femur, and tibia and associated coordinate axes were registered to the bone positions on the low-resolution scans to determine the patellar motion as a function of knee flexion angle. Hierarchical modeling was used to identify group differences in patterns of patellar spin, tilt, and lateral translation. RESULTS: No differences in the overall pattern of patellar motion were observed among groups (p>0.08 for all global maximum likelihood ratio tests). Features of patellar spin and tilt patterns varied greatly between subjects across all three groups, and no significant group differences were detected. At 19 degrees of knee flexion, the patellae in the group with patellofemoral pain and clinical evidence of malalignment were positioned an average of 2.25 mm more laterally than the patellae in the control group, and this difference was marginally significant (p=0.049). Other features of the pattern of lateral translation did not differ, and large overlaps in values were observed across all groups. CONCLUSIONS: It cannot be determined from our cross-sectional study whether the more lateral position of the patella in the group with clinical evidence of malalignment preceded or followed the onset of symptoms. It is clear from the data that an individual with patellofemoral pain syndrome cannot be distinguished from a control subject by examining patterns of spin, tilt, or lateral translation of the patella, even when clinical evidence of mechanical abnormality was observed.     

股四头肌对髌股关节影响的临床和实验观察

目的　从临床和实验二个方面研究股四头肌对髌股关节运动的影响。方法　对一组 2 6例 5 2膝患者进行动力性CT检查 ,了解股四头肌收缩状态对髌股关节排列的影响 ;对一组标本进行生物力学实验 ,用压敏片技术直观地测得股四头肌肌力变化对髌股关节接触压力的影响。结果　静力性CT检查发现有 12膝髌骨半脱位和 14膝髌骨外倾 ,其余病例动力性CT检查又发现有 2 1膝在股四头肌收缩状态下髌骨半脱位 ,9膝髌骨外倾。力学实验中发现随股内侧肌肌力下降髌股接触面趋向外侧。结论　股四头肌各肌组的肌力不平衡对髌股关节的接触压力及髌骨位置有较大的影响 ,临床上应重视对股四头肌肌力的恢复。     

髌股关节排列异常的CT检查

对髌股关节进行ＣＴ测量,确定有无髌股排列异常。方法 对一组２０例４０侧膝关节进行ＣＴ检查,分别在股四头股收缩和松驰状况下扫描,对ＣＴ图像进行测量。结果４０膝中有１０膝为静力性骨外侧半脱位,另３０膝中有１６膝为动力性髌骨半脱位;４０膝中１１膝为性髌骨外倾,另有７膝为动力性髌骨外倾。     

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.     

Correction of Patellofemoral Malalignment With Patellofemoral Arthroplasty

Background

The goal of patellofemoral arthroplasty (PFA) is to replace damaged cartilage and correct underlying deformities to reduce pain and prevent maltracking. We aimed to determine how PFA modifies patellar height, tilt, and tibial tuberosity-trochlear groove (TT-TG) distance. The hypothesis was that PFA would correct trochlear dysplasia or extensor mechanism malalignment.

Patellofemoral Pain Disorders: Evaluation and Management

Patellofemoral pain disorders can be difficult to diagnose. Careful attention to the history and physical examination is central to accurate diagnosis. Standardized office radiographs are sufficient in most cases. Computed tomography of the patellofemoral joint (precise midpatellar transverse images through the posterior femoral condyles with the knee at 15, 30, and 45 degrees of knee flexion) will provide valuable objective information regarding subtle abnormalities of patellar alignment. Magnetic resonance imaging and radionuclide scanning may be helpful in selected cases. By differentiating between rotational (tilt) and translational (subluxation) components of patellar malalignment, the clinician will be better able to prescribe appropriate treatment. It is also extremely important to localize and quantitate articular and retinacular abnormalities. While nonoperative treatment is usually successful, surgery is sometimes required. Lateral release will relieve tilt and associated pain in the lateral retinaculum. Realignment of the extensor mechanism, usually at the level of the tibial tubercle, is necessary to control lateral tracking (subluxation) of the patella. If there is lateral or distal medial articular damage related to chronic lateral tilt and/or subluxation, shift of the tibial tubercle will help to unload damaged cartilage while realigning the extensor mechanism.     

Editorial Commentary: Medial Patellofemoral Ligament Reconstruction for Recurrent Patellar Instability—Single or Double Bundle: Does It Really Matter?

Medial patellofemoral ligament reconstruction is considered by most surgeons to be the standard of care for patients with recurrent lateral patellar instability, although the choice of how and when to address concomitant bony pathology (trochlear dysplasia, patella alta, or coronal-plane malalignment—elevated tibial tubercle–trochlear groove distance) remains unclear. Medial patellofemoral ligament reconstruction works to re-establish the primary static restraint to lateral translation of the patella and reduce the risk of recurrent dislocation. Regardless of graft choice or construct, this operation works well to prevent recurrent instability. Despite the low recurrent instability rates, several significant complications can still occur, one of the most serious being patellar fracture. We continue to look for ways to improve stability and decrease risk with this operation.     

Patellar osteotomy and Albee's procedure for dysplastic patellar instability

Four patients with symptomatic patellar instability and dysplasia of the patella and femoral trochlea had a dorsal closed-wedge intraarticular sagital plane patellar osteotomy and elevation of lateral femoral condyle-Albee's procedure. All patients also had a "Modified Fulkerson-Elmslie Trillat" osteotomy of the tibial tuberosity, along with a proximal realignment-lateral release and medial plication either prior to or at the time of index surgery of patellar osteotomy and Albee's procedure. At a mean follow-up of 1 (range 3 1/2–1) year, all patients had a stable patellofemoral joint. Mean loss of range of terminal flexion was 15° (range10–20°). All patients had residual patellofemoral pain, and the results at best can be described as fair. The results of this series are encouraging in this complex group of patients with patellofemoral trochlear dysplasia with patellar instability, and we do recommend this procedure as a palliative procedure in this group of patients.     

Biomechanical Consequences of Patellar Component Medialization in Total Knee Arthroplasty

The optimal amount of patellar component medialization in knee arthroplasty is unknown. We measured the impact, on patellofemoral kinematics and contact force distribution, of 0.0-, 2.5-, and 5.0-mm patellar component medialization in 7 cadaveric specimens implanted with knee arthroplasty components. The knees were flexed dynamically in a weight-bearing rig. Medialization led to lateral shift of the patellar bone, slight medial shift of the patellar component in the femoral groove, lateral tilt of the patella, reduced patellofemoral contact force in later flexion, and lateral shift of the center of pressure in early flexion. Effects on shift and tilt were proportional to the amount of medialization. As a result of this investigation, we recommend medializing the patellar component slightly—on the order of 2.5 mm.     

Trochleoplasty and medial patellofemoral ligament reconstruction for recurrent patellar dislocation

We report a case of recurrent patellar dislocation with high-grade trochlear dysplasia which persisted despite two previous operations. We did a Dejour''s sulcus deepening trochleoplasty, medial patellofemoral ligament reconstruction, and lateral retinacular release. Trochleoplasty and medial patellofemoral ligament reconstruction is required in patients with high grade trochlear dysplasia.     

复合软组织手术对儿童习惯性髌骨脱位髌股关节适应性的影响

目的 研究复合软组织手术治疗不同年龄段儿童习惯性髌骨脱位后,髌股关节适应性的变化情况.方法 回顾性分析2000至2007年收治的习惯性髌骨脱位患儿73例.男24例,女49例;平均年龄7.1岁(3～15岁);单侧47例,双侧26例.按照年龄分为A、B两组:A组年龄3～8岁(包括8岁),24例(30膝);B组年龄8～15岁,49例(69膝).复合软组织手术包括膝关节外侧充分松解、内侧紧缩、髌腱半腱上点移位(Roux-Goldthwait手术)和股内侧肌止点下移术.术前及随访中分别行髌骨轴位和侧位X线检查,测量股骨滑车角、髌骨高度、髌骨-滑车适配角及髌骨倾斜角(Laurin角)的变化情况,以评价髌股关节适应性.结果 73例患儿均获随访,平均随访38个月(25～98个月).末次随访时髌骨脱位均无复发,其中2例发生髌骨内侧脱位.股骨滑车角:A组由术前的150.1°±5.1°改善为144.3°±6.0°,手术前后差异有统计学意义(P＜0.05);B组手术前后差异无统计学意义(P＞0.05).其余测量指标在两组均无显著变化.结论 复合软组织手术对儿童习惯性髌骨脱位髌股关节的塑型有影响,对于手术年龄在8岁以下儿童可以明显促进股骨髁的发育,降低股骨滑车角,改善髌股关节适应性;8岁以上儿童在随访期内股骨滑车角的变化不显著,髌股关节适应性改变不明显.     

The role of trochlear dysplasia in patellofemoral instability

Trochlear dysplasia is characterized by abnormal trochlear morphology and a shallow groove. It is associated with recurrent patellar dislocation, but it is unclear whether the dysplasia is congenital, the result of lateral tracking and chronic instability, or caused by a combination of factors. Lateral radiographs elucidate the crossing sign and characteristic trochlear prominence. Recurrent patellofemoral instability is multifactorial, and each component must be considered in determining treatment. Managing other factors associated with recurrent instability may compensate for a deficient trochlea and provide stability. Medial patellofemoral ligament reconstruction is recommended for patellofemoral instability in the presence of trochlear dysplasia in patients without patella alta or increased tibial tubercle-trochlear groove distance. Trochleoplasty should be reserved for severe dysplasia in which patellofemoral stability cannot otherwise be obtained.     

Patellaposition und Patellofemoralarthrose nach unikompartimentellem Kniegelenkersatz

Background

Changes of patellar position (height, tilt, and shift) and arthritis of the patellofemoral joint might potentially influence outcome after unicompartmental knee replacement.

Objectives

The purpose of this work is to evaluate the influence of the aforementioned parameters on postoperative outcome.

Methods

Literature analysis via PubMed.

Results

A total of 12 relevant studies (three about Patellar height, two about patellar tilt and shift, seven about patellofemoral osteoarthritis) could be identified. Regarding Patellar height, two out of three studies demonstrated a postoperative decrease. With regard to patellar tilt and shift, only one study identified postoperative lateralization of the patella to be a predictor for poor outcome. The radiological appearance of arthritis of the patellofemoral joint does not significantly influence postoperative knee function except for cases where only the lateral patellar facet is affected. Anterior knee pain has no influence on clinical outcome.

Conclusion

Literature data do not allow for a precise statement about the possible influence of patellar position on the outcome after unicompartmental knee replacement. With proper patient selection, good results can be achieved despite patellofemoral osteoarthritis.     

The lateral condyle index: a new index for assessing the length of the lateral articular trochlea as predisposing factor for patellar instability

The central trochlea has been considered as the major location of dysplasia. The purpose of this study was to investigate the influence of the lateral trochlea on patellar stability and to establish a new method for measuring the lateral trochlea on sagittal magnetic resonance (MR) images. Twenty-eight knees of 23 patients suffering from lateral patellar subluxation (12 knees with radiological signs of central trochlear dysplasia) and of 46 patients without patellofemoral complaints (without central trochlear dysplasia) were analysed. The lateral condyle index was designed to measure the lateral trochlea by comparing the anterior cartilaginous trochlea (a) and the posterior aspect (p) [(a:p)× 100]. The lateral condyle index showed high interrater reliability (r = .94) and was significantly (p < 0.001) lower in symptomatic patients (86%) than in the control group (93%). These results show high clinical relevance of the lateral trochlea as another factor for patellar instability.