Arthroscopic surgery and the lateral release for patellofemoral disorders

A 30° arthroscope, when placed from a portal 4 cm proximal to and in line with the medial edge of the patella,approaches the trochlea at a 30° angle, providing a straight-on view of the patellofemoral joint without distortion. By routinely placing the arthroscope through this portal, patellar tracking can be evaluated and patellar malalignment documented and corrected under direct vision. When a lateral release is performed, the scope is in the proximal superomedial portal and the electrosurgical unit is through the anterolateral portal without the tourniquet being inflated. If subluxation remains after lateral release is performed, the degree of medial imbrication to be done is judged arthroscopically to prevent undercorrecting or over-correcting the patellar realignment. When oblique anteromedialization osteotomy of the tibial tubercle is done, the arthroscopic view assists in determining the degree of medialization of the tubercle to be performed. The maximum medialization is believed to be one half the width of the tubercle and fixed with AO small fragment cancellous compression screws. A lateral release is always performed with this procedure and, if it fails to provide patellar realignment, medial imbrication is added. Postoperative positioning in flexion assists the recovery.     

Reducing the lateral force acting on the patella does not consistently decrease patellofemoral pressures

BACKGROUND: Extensor mechanism procedures that decrease the lateral component of the patellar tendon or quadriceps force acting on the patella do not consistently reduce pain. HYPOTHESIS: Patellofemoral treatments do not consistently decrease patellofemoral pressures because of variations in the moments acting on the patella. STUDY DESIGN: Computer simulation study. METHODS: Computational models of 4 knees were constructed to characterize the patellofemoral pressure distribution during simulated squatting from 40 degrees to 90 degrees. The knees were given an initial Q angle of 25 degrees. Patellofemoral treatments were simulated by increasing the percentage of the quadriceps force applied by the vastus medialis by 50% and by medializing the tibial tuberosity to decrease the Q angle to 15 degrees. RESULTS: Decreasing the Q angle caused a larger decrease in the lateral component of the force applied by the quadriceps and patellar tendon than did increasing the force applied by the vastus medialis and, therefore, was more effective at decreasing patellofemoral pressures and the force needed to resist lateral subluxation. Both treatments also decreased the moments acting to rotate the distal patella laterally and tilt the patella laterally during flexion. Variations in these moments increased patellofemoral pressures for some knees. CONCLUSIONS: Treatments that reduce patellofemoral subluxation can have an unexpected influence on patellofemoral pressures because of the moments acting on the patella. CLINICAL RELEVANCE: Extensor mechanism procedures that restore patellofemoral stability may not provide pain relief.     

Articular cartilage contact pressure after tibial tuberosity transfer. A cadaveric study

Medial transfer of the tibial tuberosity has been commonly used for treatment of recurrent dislocation of the patella and patellofemoral malalignment. In this study, six fresh human cadaveric knees were used. Static intrajoint loads were recorded using Fuji Prescale pressure-sensitive film for contact pressure and contact area determination in a closed kinetic chain knee testing protocol. Peak pressures, average contact pressures, and contact areas of the patellofemoral and tibiofemoral joints were calculated on native intact knee specimens and after tibial tuberosity transfer. All native intact knee specimens had a normal Q angle. Medialization of the tibial tuberosity significantly increased the patellofemoral contact pressure. Medial displacement of the tibial tuberosity also significantly increased the average contact pressure of the medial tibiofemoral compartment and changed the balance of tibiofemoral joint loading. The results of our study suggest that caution should be used when transferring a patellar tendon in the face of a preexisting normal Q angle as this will result in abnormally high peak pressure within the tibiofemoral joint. Overmedialization of the tibial tuberosity should be avoided in the varus knee, the knee after medial meniscectomy, and the knee with preexisting degenerative arthritis of the medial compartment.     

Distal realignment for recurrent patellar instability

There are multiple approaches to treating the patient presenting with recurrent patellar instability. Current thought emphasizes identifying the specific pathology allowing the instability, and then seeking to address that specific problem. Patients who show lateral positioning of the tibial tubercle as their isolated source of pathology may have improved outcomes if that particular problem is corrected through distal tibial tubercle medialization realignment. If these patients have patellar chondrosis, in addition to medialization, anteriorization is added in the manner of anteromedialization.     

The effect of tibial tuberosity realignment procedures on the patellofemoral pressure distribution

Purpose

The study was performed to characterize the influence of tibial tuberosity realignment on the pressure applied to cartilage on the patella in the intact condition and with lesions on the lateral and medial facets.

Methods

Ten knees were loaded in vitro through the quadriceps (586 N) and hamstrings (200 N) at 40°, 60°, and 80° of flexion while measuring patellofemoral contact pressures with a pressure sensor. The tibial tuberosity was positioned 5 mm lateral of the normal position to represent lateral malalignment, 5 mm medial of the normal position to represent tuberosity medialization, and 10 mm anterior of the medial position to represent tuberosity anteromedialization. The knees were tested with intact cartilage, with a 12-mm-diameter lesion created within the lateral patellar cartilage, and with the lateral lesion repaired with silicone combined with a medial lesion. A repeated measures ANOVA and post hoc tests were used to identify significant (P < 0.05) differences in the maximum lateral and medial pressure between the tuberosity positions.

Results

Tuberosity medialization and anteromedialization significantly decreased the maximum lateral pressure by approximately 15% at 60° and 80° for intact cartilage and cartilage with a lateral lesion. Tuberosity medialization significantly increased the maximum medial pressure for intact cartilage at 80°, but the maximum medial pressure did not exceed the maximum lateral pressure for any testing condition.

Conclusions

The results indicate that medializing the tibial tuberosity by 10 mm reduces the pressure applied to lateral patellar cartilage for intact cartilage and cartilage with lateral lesions, but does not overload medial cartilage.     

Trochlear contact pressures after anteromedialization of the tibial tubercle

BACKGROUND: Anteromedialization is recommended for cartilage restoration of patellofemoral defects, with the presumption that it decreases contact pressures across the trochlea. No study has evaluated pressures on the trochlear side of the patellofemoral joint after anteromedialization of the tibial tubercle. HYPOTHESIS: Anteromedialization of the tibial tubercle decreases contact pressure across the trochlea. STUDY DESIGN: Controlled laboratory study. METHODS: Ten cadaveric knees were tested by placing an electroresistive pressure sensor on the femoral side of the patellofemoral joint. A validated model of nonweightbearing resisted extension was simulated by loading the extensor mechanism at 89.1 N and 178.2 N. Knees were tested 3 times per load at 30 degrees , 60 degrees , 90 degrees , and 105 degrees . The center of force and pressure across the patellofemoral articulation were compared before and after a reproducible and consistent anteromedialization. RESULTS: The mean center of force shifted medially after anteromedialization at 89.1 N and 178.2 N. At 89.1 N, the mean total contact pressure decreased significantly (P < .05) at all angles, and at 178.2 N, it decreased significantly at 30 degrees , 60 degrees , and 90 degrees of knee flexion. The mean lateral trochlear contact pressure decreased significantly (P < .05) at all flexion angles at both 89.1 N and 178.2 N. The mean central trochlear contact pressure decreased significantly (P < .05) at 30 degrees with the 89.1-N and 178.2-N loads but increased significantly (P < .05) at 90 degrees with the 89.1-N load. The mean medial trochlear contact pressure increased significantly (P < .05) at all flexion angles at 89.1 N and 178.2 N. CONCLUSION: Anteromedialization shifts the contact force to the medial trochlea and decreases the mean total contact pressure. CLINICAL RELEVANCE: Anteromedialization decreases the mean total contact pressure while shifting contact pressure toward the medial trochlea. This study suggests that anteromedialization is appropriate for unloading the lateral trochlea. However, this procedure appears to have minimal benefit on central chondral defects, and it may actually increase the load in patients with medial defects.     

Osteotomies in patello-femoral instabilities

Patellar instability is defined by clinical and radiologic criteria. The surgical treatment is aimed at restoring the congruence of the patellofemoral articulation and correcting extensor mechanism malalignment, to prevent recurrence of dislocation. The standard soft-tissue procedures are lateral release and vastus medialis advancement and medial patello femoral ligament plasty. Bony procedures are frequently performed in addition to soft-tissue surgery, to realign the extensor mechanism by means of tibial tubercle medialization, or to correct the patellar index in patella alta. In a smaller number of patients, the trochlea may be reshaped, by elevating the lateral trochlear facet or by lowering the floor of the sulcus. The morphologic abnormalities encountered are studied and quantified in the light of preoperative investigations (conventional radiographs and computed tomography), and addressed at surgery using the technique or techniques most appropriate for the management of the individual patient's pattern.     

The effects of weight-bearing conditions on patellofemoral indices in individuals without and with patellofemoral pain syndrome

Objective

The purpose of this study is to evaluate differences between the patellofemoral joint indices after supine, non-weight-bearing and standing position, and weight-bearing Merchant view radiographs in individuals without and with patellofemoral pain syndrome (PFPS).

Materials and methods

Radiographs of 44 knees without PFPS and 51 knees with PFPS were retrospectively evaluated. In both positions, the non-weight-bearing and weight-bearing Merchant views, patellar indices such as patellar tilt angle, lateral patellofemoral angle, lateral subluxation distance, lateral patellar displacement, and congruence angle were measured, respectively. The differences between the patellofemoral joint indices in knees with and without PFPS were analyzed using univariate and multivariate regression analysis, in regards to correlation factors.

Results

The patellar tilt angle (p?=?0.0002), lateral subluxation distance (p?=?0.038), lateral patellar displacement (p?=?0.0004), and congruence angle (p?<?0.0001) on the weight-bearing Merchant view was significantly decreased in normal knees without PFPS. In pathologic knees with PFPS, the patellar tilt angle (p?<?0.0001), lateral subluxation distance (p?<?0.0001), lateral patella displacement (p?<?0.0001), and congruence angle (p?<?0.0001) on weight-bearing Merchant view was also significantly decreased. The difference between the patellofemoral indices was significantly more in knees specifically with PFPS (p?<?0.05).

Conclusions

These results suggest that patellofemoral indices measured during non-weight-bearing supine position do not sufficiently represent the patellofemoral kinematics during normal weight-bearing activities. We conclude that this study establishes the clinical significance and relevance of assessing the patellofemoral kinematics by weight-bearing, standing Merchant view radiographs, when evaluating patients with patellofemoral problems.     

Long patellar tendon: radiographic sign of patellofemoral pain syndrome--a prospective study.

The position of the patella was studied prospectively in both knees of 45 consecutive patients (21 male and 24 female patients aged 16-48 years who were competitive [n = 17] or recreational [n = 28] athletes) who had unilateral patellofemoral pain syndrome without symptoms or signs of patellar instability at initial examination. In each knee, standardized anteroposterior, lateral, and tangential radiographs were obtained and six indexes of patellar position (the ratio of the patellar tendon to the greatest diagonal length of the patella, sulcus angles, lateral patellofemoral angle, lateral patellar displacement, patellofemoral index, and knee angle) were measured. When healthy and affected knees were compared, high riding of the patella due to long patellar tendon (patella alta) was the only definite finding in the affected knees. The shape of the intercondylar sulcus and the mediolateral position of the patella were identical in both knees, providing no evidence for patellofemoral incongruence or lateral patellar tilt. Results of this study strongly suggest that idiopathic retropatellar pain is closely associated with patella alta.     

Evaluation of the patellofemoral joint with kinematic MR fluoroscopy

OBJECTIVE: The aim of this study was to evaluate the diagnostic effectiveness of kinematic magnetic resonance fluoroscopy (KMRF) on patients with patellofemoral incongruency. MATERIALA AND METHODS: 17 patients (20 knees) and 10 healthy volunteers (20 knees), all men (mean age 29.4 years, S.D. 9, range 16-50), were included to our study. Only male subjects were studied because of potential biomechanical differences between sexes. KMRF was used to perform kinematic MR imaging of patellar alignment and tracking in 10 healthy subjects and 17 patients with a provisional clinical diagnosis of abnormal patellofemoral joints. The patellofemoral joints were examined with the knee in different angles of active flexion. At each knee position, real time kinematic and axial MRF image was used to focus on the sagittal plane, followed by an axial image focused through the middle of the patella. Three angles were measured: patellar tilt angle (PTA), sulcus angle (SA) and congruence angle (CA). RESULTS: Five patterns of malalignment were identified and studied. Two patellofemoral joints were normal, 10 had lateralization of the patella, 2 had patellar tilt, 2 had lateralization and patellar tilt (i.e. excessive lateral pressure syndrome) and 4 had medialization of the patella. CONCLUSION: KMRF is an effective method in evaluating patellofemoral incongruency. Short time duration of investigation, ability to get nearly real time images, suitable temporal contrast resolution and investigation from very different angles of knee are important advantages of the method.     

Anteromedial tibial tubercle transfer without bone graft

We followed 30 patients for more than 2 years after anteromedial tibial tubercle transfer for persistent patellofemoral pain associated with patellar articular degeneration. Twelve of these patients were followed more than 5 years. We report 93% good and excellent results subjectively and 89% good and excellent results objectively. The quality of improvement was sustained in all 12 of the patients who were evaluated again after more than 5 years from surgery. When examined separately, 75% of those patients with advanced patellar arthrosis achieved a good result; none of these patients achieved an excellent result. Postoperative continuous passive motion has markedly reduced the incidence of stiffness. Serious complications such as compartment syndrome, infection, and skin slough were avoided completely in 51 consecutive cases. Patellofemoral contact pressure studies in five cadaver knees have shown that anteromedial tibial tubercle transfer can provide substantial reduction of patellofemoral contact stress while helping to balance medial and lateral facet pressures. This surgical procedure is mechanically and clinically successful for alleviating intractable pain related to patellar malalignment and articular degeneration. This procedure enables the majority of appropriately selected patients with malalignment and patellar articular degeneration to resume increased levels of activity with substantially diminished pain.     

Patellar thickness and lateral retinacular release affects patellofemoral kinematics in total knee arthroplasty

Purpose

To study the effect of increasing patellar thickness (overstuffing) on patellofemoral kinematics in total knee arthroplasty and whether subsequent lateral retinacular release would restore the change in kinematics.

Methods

The quadriceps of eight fresh-frozen knees were loaded on a custom-made jig. Kinematic data were recorded using an optical tracking device for the native knee, following total knee arthroplasty (TKA), then with patellar thicknesses from ?2 to +4 mm, during knee extension motion. Staged lateral retinacular releases were performed to examine the restoration of normal patellar kinematics.

Results

Compared to the native knee, TKA led to significant changes in patellofemoral kinematics, with significant increases in lateral shift, tilt and rotation. When patellar composite thickness was increased, the patella tilted further laterally. Lateral release partly corrected this lateral tilt but caused abnormal tibial external rotation. With complete release of the lateral retinaculum and capsule, the patella with an increased thickness of 4 mm remained more laterally tilted compared to the TKA with normal patellar thickness between 45° and 55° knee flexion and from 75° onwards. This was on average by 2.4° ± 2.9° (p < 0.05) and 2.°9 ± 3.0° (p < 0.01), respectively. Before the release, for those flexion ranges, the patella was tilted laterally by 4.7° ± 3.2° and 5.4° ± 2.7° more than in the TKA with matched patellar thickness.

Conclusion

Patellar thickness affects patellofemoral kinematics after TKA. Although lateral tilt was partly corrected by lateral retinacular release, this affected the tibiofemoral kinematics.

Level of evidence

IV.     

Biomechanical analysis of flat and oblique tibial tubercle osteotomy for recurrent patellar instability.

Both flat (Elmslie-Trillat) and oblique (Fulkerson) osteotomy techniques are successful in treating patellar instability episodes by moving the tibial tubercle medially. The oblique osteotomy also results in anterior displacement that decreases patellofemoral forces. Recent reports have described proximal tibial fractures occurring during early weightbearing after oblique osteotomy. We performed oblique and flat osteotomies on 13 pairs of fresh-frozen cadaveric knees. The knees were then tested to failure on a materials testing system by exerting a load through the quadriceps tendon at a rate of 1000 N/sec to simulate a stumble injury. The failure mechanism for flat osteotomies was more likely to be tubercle "shingle" fracture, while oblique osteotomies more frequently failed through a tibial fracture or fixation failure in the posterior tibial cortex. Mean load to failure was significantly higher in the flat osteotomy specimens (1639 N versus 1166 N), as was total energy to failure (224 N.m versus 127 N.m). There was no significant difference in stiffness (87 N/cm versus 74 N/cm). We recommend the flat osteotomy for patients with isolated recurrent patellar instability and the oblique osteotomy in patients who have concomitant patellofemoral pain or articular degenerative changes. When an oblique osteotomy is used, we recommend postoperative brace protection and restricted weightbearing until the osteotomy heals.     

Incidence and radiologic predictor of postoperative patellar instability after Fulkerson procedure of the tibial tuberosity for recurrent patellar dislocation

Purpose

Excellent results of anteromedialization of the tibial tuberosity for recurrent patellar dislocation have been reported; however, the contribution of the preoperative anatomic factors to postoperative patellar instability has not been well established. The purpose of this study was to investigate the mid-term results and the incidence of postoperative patellar instability after Fulkerson procedure for recurrent patella dislocation, and to determine the radiologic predictor of the postoperative patellar instability.

Methods

Sixty-two knees of 41 patients underwent Fulkerson procedure with or without lateral retinacular release for recurrent patellar dislocation and were followed-up for 85–155 months. Predisposing anatomic factors for recurrent patellar dislocation were evaluated preoperatively, including valgus knee alignment (femorotibial angle), patella alta (Insall–Salvati ratio), trochlear dysplasia (trochlear depth), lateral patellar displacement (congruence angle) and lateral malposition of the tibial tuberosity (tibial tuberosity-trochlear groove distance). The relationship between the measurements of anatomic factors and postoperative patellar instability, which was defined by the patellar re-dislocation or residual apprehension after surgery, was analyzed.

Results

The Fulkerson score and the Kujala score were significantly improved from the median of 65 (35–80) points and 68 (36–82) points preoperatively to 95 (60–100) points and 92 (57–100) points at the final follow-up, respectively. Three knees (4.8%) experienced postoperative patellar re-dislocation and 4 knees (6.5%) showed the positive apprehension sign at the final follow-up. The statistical analysis showed that the postoperative patellar instability correlated with only patella alta.

Conclusion

Patella alta was the only predictor of postoperative patellar instability after Fulkerson procedure. These results indicated that isolated Fulkerson procedure should not be indicated for recurrent patellar dislocation with severe patella alta.

Level of evidence

Case–control study, Level III.     

MRI对复发性髌骨不稳的解剖学危险因素的测量与评估

目的 定量测量并评估复发性髌骨不稳患者的髌股解剖学相关指标及其首要危险预测因素.方法 对52例经保守治疗失败的复发性髌骨不稳的年轻患者患膝进行回顾性MRI图像分析,测量指标包括描述髌骨轨迹的3个参数:髌骨偏移指数(BSO)、滑车适合角(CA)和髌骨倾斜角(PTA)以及描述髌股关节解剖学的7个参数:滑车沟角度(SA)、股骨外侧滑车倾斜角(LTI)、股骨滑车面对称性、股骨滑车深度、ISR(Insall-Salvati Ratio)、C-D(Caton-Deschamps index)和胫骨结节-股骨滑车沟(TT-TG)距离,并对测量结果进行Pearson's相关及多元逐步回归分析.结果 髌骨轨迹异常与LTI、TT-TG距离和ISR均存在显著相关性,而与股骨滑车深度、SA、滑车面对称性及C-D之间无统计学相关性或仅有部分指标相关.解剖学参数LTI、TT-TG距离及ISR构成的回归模型对BSO、CA和PTA的拟合优度R2分别为0.58、0.47和0.43(P<0.001),其中LTI的标准化回归系数β值最大,其次为TT-TG距离和ISR.结论 伸膝位时,MRI定量测量的髌股解剖学相关参数可以一定程度上解释复发性髌骨轨迹的外移和倾斜,其中:LTI是导致髌骨轨迹异常的解剖学相关指标中的首要危险预测因素,其次分别是TT-TG距离及ISR.     

Decreased ratios of lateral to medial patellofemoral forces and pressures after lateral retinacular release and gender knees in total knee arthroplasty

Purpose

To demonstrate that lateral to medial patellofemoral force and pressure ratios could be a surrogate marker of retinacular tension and patellar tracking.

Methods

The patellofemoral forces of six knees from three fresh-frozen half-body female cadavers were evaluated with a capacitive sensor under simulated operative conditions in six staged clinical scenarios: native knees, knee arthroplasty without patellar resurfacing, resurfaced knee and patella, resurfaced knee and patella with lateral release, gender-specific knee arthroplasty with patella resurfacing, and gender-specific knee arthroplasty with lateral release. Maximum force and peak pressure were simultaneously recorded during three to four ranges of motion. Average values were compared between lateral and medial patellofemoral compartments as an objective measure of patellar tracking for the different settings.

Results

Significant differences in lateral and medial force and pressure differentials were seen in most scenarios despite clinically normal patellar tracking. Lateral to medial ratios of maximum force and peak pressure significantly increased after TKA (2.9, 2.1) and after patella resurfacing (2.8, 2.6) compared to the native knee (1.6, 1.8). Addition of a lateral release in resurfaced knees decreased the ratio of lateral to medial patellofemoral forces and pressures as did gender knee arthroplasty (1.5 and 1.1, 2 and 1.3, respectively). Pressure and force values most closely resembled the native knee in the resurfaced knee/resurfaced patella with lateral release and in the gender knee arthroplasty scenarios.

Conclusions

Use of lateral to medial patellofemoral force ratios as a surrogate objective marker for patellar tracking was validated in this study by decreasing ratios observed after lateral release in TKA and with gender-specific implants.     

The effect of reconstruction of the medial patellofemoral ligament on patellar tracking

We evaluated patellar tracking in six cadaveric knees with the medial restraints intact and then sectioned to determine their contribution to lateral translation of the patella with and without a lateral force on the patella. The medial patellofemoral ligament was then reconstructed with a gracilis tendon graft and patellar tracking was again evaluated. The knees were extended using a materials testing machine, and patellar tracking was measured with a position sensing system. With no lateral force applied to the patella, patellar tracking was unaffected by the presence or absence of the medial restraints or by reconstruction of the medial patellofemoral ligament. With a lateral force applied to the patella, patellar tracking was changed significantly by the loss of the medial restraints. Normal patellar tracking was substantially restored by reconstruction of the medial patellofemoral ligament.     

Effect of patellar tendon shortening on tracking of the patella

BACKGROUND: Although 10% postoperative patellar tendon shortening after bone-patellar tendon-bone autograft reconstruction of the anterior cruciate ligament has been reported, there are no published studies assessing the effect of shortening on patellofemoral joint biomechanics under physiological loading conditions. PURPOSE: To investigate the influence of patellar tendon shortening on patellofemoral joint biomechanics. STUDY DESIGN: Controlled laboratory study. METHODS: The authors evaluated the patellofemoral contact area, the location of contact, and the patellofemoral joint reaction force and contact stresses in 7 cadaveric knees before and after 10% patellar tendon shortening. Shortening was achieved using a specially designed device. Experimental conditions simulating those occurring during level walking were employed: physiological quadriceps loads and corresponding angles of tibial rotation were applied at 15 degrees , 30 degrees , and 60 degrees flexion of the knee. Patellofemoral joint contact areas were measured before and after shortening using the silicone oil-carbon black powder suspension squeeze technique. RESULTS: After patellar tendon shortening, patellofemoral joint contact areas were displaced proximally on the patellar surface and distally on the femoral surface. Although the contact area increased by 18% at 15 degrees of knee flexion (P = .04), no significant change occurred at 30 degrees or 60 degrees of knee flexion (P > .05). Patellofemoral contact stress remained unchanged after patellar tendon shortening (P > .05) at each flexion angle. CONCLUSION: Our results suggest that a 10% shortening of the patellar tendon does not alter patellar contact stresses during locomotion. It is not clear whether apparent changes in contact location in all positions and contact area at 15 degrees would have clinical consequences.     

Effect of bracing on patellar kinematics in patients with patellofemoral joint pain

PURPOSE: Bracing is commonly used to correct patellar malalignment syndromes. However, there are little objective data documenting the effect of such supports on patellofemoral joint relationships. The purpose of this study was to assess the effectiveness of an elastic patellofemoral sleeve brace in altering patellar tracking in subjects with patellofemoral pain. METHODS: Ten female subjects (12 patellofemoral joints) between the ages of 17 and 46 participated in this study. All subjects had a diagnosis of patellofemoral pain and demonstrated lateral patellar tracking based on magnetic resonance imaging (MRI) assessment. Each subject underwent kinematic MRI of the patellofemoral joint through a range of 45 to 0 degrees of knee flexion against a resistance of 15% body weight. Imaging was performed with and without a patellofemoral joint brace (Bauerfeind Genutrain P3 brace, Atlanta, GA). Measurement of medial/lateral patellar displacement, medial/lateral patellar tilt, and the depth of the trochlear groove (sulcus angle) were obtained with midpatellar image sections at 45, 36, 27, 18, 9 and 0 degrees of knee flexion. RESULTS: No statistically significant differences in medial/lateral patellar displacement or tilt were found between braced and unbraced trials across all knee flexion angles (P < 0.05). A small but statistically significant increase in sulcus angle was found across all knee flexion angles with the braced trials (P > 0.05). CONCLUSIONS: These results do not support the hypothesis that the brace used in this study corrects patellar tracking patterns in subjects with patellofemoral pain. However, the increased sulcus angle indicates a change in patella position within the trochlea. It is possible that the clinical improvements seen with bracing may be the result of subtle differences in joint mechanics and not gross changes in alignment.     

股骨髁髌股、胫股关节运动重叠接触区域及其生物力学测定

目的 :明确膝关节运动时胫骨、髌骨与股骨髁接触的重叠区域 ,测量并比较分析重叠区域内髌股、胫股关节各自接触压大小及分布特点 ,探讨髌股关节置换术中股骨滑车假体长度的设计。方法 :收集 8具新鲜膝关节尸体标本 ,在Instron 85 0 1生物力学测试仪上构建实验平台 ,模拟生理状态下膝关节站立到下蹲屈膝的过程 ,采用染色法描记重叠区域、压敏法测量髌股、胫股关节在该区域接触压。结果 :股骨髁关节面存在髌股、胫股关节运动重叠接触区域 ,范围大致相当股骨髁髌股关节接触区域内、始于屈膝 75°髌股接触部的后部分区域 ;重叠区域内髌股、胫股关节各自接触压测定显示 ,前者的接触压明显高于后者。结论 :股骨滑车假体的有效长度应涵盖髌股关节在股骨髁所有接触区域。