Patellar Tracking Research Articles

The Elmslie-Trillat Procedure for Recurrent Patellar Subluxation After Total Knee Arthroplasty

Patellofemoral problems are the most common complications after total knee arthroplasty (TKA). We report a patient who had patellar subluxation twice within 7 months after primary TKA. Postoperative radiographs and computed tomography scans revealed a valgus knee with no evidence of malposition of the prostheses. To eliminate the recurrent patellar subluxation, we finally performed an Elmslie-Trillat procedure in combination with extensive lateral release and succeeded in achieving normal patellar tracking. At 1-year postoperative follow-up, the patient was satisfied with the results. The patella tracked well in the femoral trochlear groove during knee flexion after the revision surgery. This procedure, in combination with lateral release, should be considered as a useful surgical treatment that can eliminate patellar subluxation after TKA in cases without component malposition.

An electromyographic exploratory study comparing the difference in the onset of hamstring and quadriceps contraction in patients with anterior knee pain

Idiopathic anterior knee pain in teenagers and young adults is a common condition. Patellar maltracking has been considered as a causative factor. The aim of our study was to investigate whether there was a difference in the timing of electromyographic (EMG) activity in the medial and lateral hamstring and quadriceps muscles of patients with anterior knee pain compared to asymptomatic control participants. This was a cross sectional observational study measuring EMG activation patterns. Two groups of participants were tested, one patient (mean age 15 years, n = 20) and one asymptomatic control (mean age 16 years, n = 17). Surface EMG (sampling rate 1000 Hz) was recorded from vastus medialis obliqus, vastus lateralis, and the medial and lateral hamstrings during three repetitions of maximal voluntary isometric contractions. The relative timing of the medial and lateral quadriceps and hamstrings was evaluated. The mean (95% confidence interval) difference between the groups in the lateral–medial hamstring onset timing was 53.8 (1.9 to 105.6) ms during the maximal contraction. An independent t test showed that this difference was statistically significant (p = 0.043). The differences between the groups in the relative VMO to VL onset did not reach statistical significance. The results of this study suggest that the lateral hamstrings contract significantly earlier in patients with AKP compared to healthy controls for this small cohort. This altered activation pattern could produce external rotation of the tibia on the femur and cause lateral patella tracking.

Technical Challenges of Total Knee Arthroplasty in Skeletal Dysplasia

Total knee arthroplasty (TKA) in patients with skeletal dysplasias is particularly challenging as a result of the anatomic variances and substantial bony deformities. Little has been written regarding technical considerations that should be made when performing TKA in skeletal dysplasia. We describe special operative considerations that must be made when performing TKA on patients with skeletal dysplasia, including implant selection and ligamentous balancing. We retrospectively reviewed 12 TKAs in eight patients with varying degrees of deformity (ranging from 30° of varus to 45° of valgus) secondary to three types of skeletal dysplasias: multiple hereditary exostosis, achondroplasia, and osteogenesis imperfecta. Clinical notes, operative records, and radiographic data were reviewed. Minimum followup was 1 year (average, 4 years; range, 1-10 years). We used customized implants in three of the 12 knees. Constrained tibial inserts were used in five knees. All 12 knees underwent releases (soft tissue or epicondylar osteotomy) to address gap balancing or patellar tracking. Average Knee Society scores improved from 35.9 preoperatively to 82.9 postoperatively and average function scores improved from 47.9 preoperatively to 96.7 postoperatively. Complications included two transient peroneal nerve palsies. Special considerations must be made with regard to implant selection and ligamentous balancing as a result of the unusual anatomy and deformities that accompany skeletal dysplasia, but the short-term clinical results reveal consistent improvements in pain and function. Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Lateral subvastus approach with osteotomy of the tibial tubercle for total knee replacement

The lateral subvastus approach combined with an osteotomy of the tibial tubercle is a recognised, but rarely used approach for total knee replacement (TKR). A total of 32 patients undergoing primary TKR was randomised into two groups, in one of which the lateral subvastus approach combined with a tibial tubercle osteotomy and in the other the medial parapatellar approach were used. The patients were assessed radiologically and clinically using measurement of the range of movement, a visual analogue patient satisfaction score, the Western Ontario McMasters University Osteoarthritis Index and the American Knee Society score. Four patients were lost to the complete follow-up at two years. At two years there were no significant differences between the groups in any of the parameters for clinical outcome. In the lateral approach group there was one complication due to displacement of the tibial tubercle osteotomy and two osteotomies took more than six months to unite. In the medial approach group, one patient had a partial tear of the quadriceps. There was a significantly greater incidence of lateral patellar subluxation in the medial approach group (3 of 12) compared with the lateral approach group (0 of 16) (p = 0.034), but without any apparent clinical detriment. We conclude that the lateral approach with tibial tubercle osteotomy is a safe technique with an outcome comparable with that of the medial parapatellar approach for TKR, but the increased surgical time and its specific complications do not support its routine use. It would seem to be more appropriate to reserve this technique for patients in whom problems with patellar tracking are anticipated.

Should the ‘no thumb technique’ be the golden standard for evaluating patellar tracking in total knee arthroplasty?

We checked intraoperative patellar tracking with both ‘towel clip technique’ and the ‘no thumb technique’ on 97 patients (167 knees) who underwent primary total knee arthroplasty to decide whether to do or not to do lateral retinacular release. Patellar tracking was assessed under pneumatic tourniquet with the no thumb technique first and re-evaluated with the towel clip technique. The tracking was graded as total contact, good contact, lateral contact and subluxation. The knees graded as total or good contact with the no thumb technique were classified into group A; those graded lateral contact or subluxation by the no thumb technique but total or good contact by the towel clip technique were classified into group B; and those graded lateral contact or subluxation by both techniques were classified into group C; in which lateral releases were performed. One hundred three, 53 and 11 knees were classified into groups A, B and C respectively. Of the 167 knees, 64 (38.3%) showed poor tracking (lateral contact or subluxation) with the no thumb technique alone. Re-evaluation of these knees with the towel clip technique significantly reduced the number with poor tracking to 11 (6.6%) knees requiring lateral retinacular release ( p < 0.05). The patients were followed up for 1 year without any patella-related complications occurring. Assessment of the patellar tracking using only the no thumb technique may overestimate the need for lateral retinacular release. The use of the no thumb technique as a screening test, and re-evaluation with the towel clip technique may reduce unnecessary lateral retinacular release.

The Effect of Closed-Kinetic Chain Exercises and Open-Kinetic Chain Exercise on the Muscle Activity of Vastus Medialis Oblique and Vastus Lateralis

Patellofemoral pain syndrome (PFPS) is one of the most prevalent musculoskeletal conditions of the lower limb. The muscle imbalance between the vastus medialis oblique (VMO) and vastus lateralis (VL) muscles is one of the main factors leading to the development of PFPS. The disparity in research and the necessity to add to the existing literature base led to the development of this study. The aim of this study was to investigate the effect of 2 closed kinetic chain exercises and 1 open kinetic chain exercise on VMO and VL muscle activity. Twenty-two healthy asymptomatic individuals participated in this study. The surface electromyography (EMG) of VMO and VL was measured and used to calculate the VMO:VL ratio during 3 different quadriceps-strengthening exercises (a double leg squat with isometric hip adduction exercise, an open kinetic chain knee extension exercise, and a lunge exercise). The double leg squat with isometric hip adduction exercise was shown to produce a significantly greater VMO:VL ratio (1.14:1) than the other 2 exercises (p = 0.015 and p = 0.005). The open kinetic chain knee extension exercises produced significantly greater activation of VL than the lunge exercise (p = 0.001 and p = 0.036). The lunge exercise produced the VMO:VL ratio (1.18:1) closest to the idealized ratio of 1:1. Potential clinical recommendations can be made proposing the lunge exercise as a key tool in early rehabilitation when restoring preferential VMO:VL ratio is essential. The double leg squat with isometric hip adduction exercise would be useful in maintaining correct patella tracking and selectively strengthening VMO.

Medial reefing versus medial patellofemoral ligament reconstruction for patellar instability

The standard surgical treatment for patellar instability has been lateral release and medial reefing proximally, with a Roux-Goldthwaite tendon transfer distally. More recently, reconstruction of the medial patellofemoral ligament (MPFL) has become popular. The aim of this study was to determine whether MPFL reconstruction improved the functional outcomes over patients treated with medial reefing. A group of 28 knees in 25 patients treated with a MPFL reconstruction were identified and matched for age and gender with 28 operated knees in 27 patients treated with a medial reefing. Clinical assessment included pre-operative and 1 year Kujala scores. Radiological assessment used the Dejour protocol. The two groups were comparable with respect to gender, age, pre-operative Kujala score, type of trochlear dysplasia, tibial tubercle–trochlear groove distance and patellar tilt angle. It was concluded that although there was better patellar tracking at 1 year with an MPFL reconstruction compared to medial reefing, there was no significant functional improvement as measured by the Kujala score.

Relationship Between Three-Dimensional Geometry of the Trochlear Groove and In Vivo Patellar Tracking During Weight-Bearing Knee Flexion

It is widely recognized that the tracking of patella is strongly influenced by the geometry of the trochlear groove. Nonetheless, quantitative baseline data regarding correlation between the three-dimensional geometry of the trochlear groove and patellar tracking under in vivo weight-bearing conditions are not available. A combined magnetic resonance and dual fluoroscopic imaging technique, coupled with multivariate regression analysis, was used to quantify the relationship between trochlear groove geometry (sulcus location, bisector angle, and coronal plane angle) and in vivo patellar tracking (shift, tilt, and rotation) during weight-bearing knee flexion. The results showed that in the transverse plane, patellar shift was strongly correlated (correlation coefficient R=0.86, p<0.001) to mediolateral location of the trochlear sulcus (raw regression coefficient β(raw)=0.62) and the trochlear bisector angle (β(raw)=0.31). Similarly, patellar tilt showed a significant association with the trochlear bisector angle (R=0.45, p<0.001, and β(raw)=0.60). However, in the coronal plane patellar rotation was poorly correlated with its matching geometric parameter, namely, the coronal plane angle of the trochlea (R=0.26, p=0.01, β(raw)=0.08). The geometry of the trochlear groove in the transverse plane of the femur had significant effect on the transverse plane motion of the patella (patellar shift and tilt) under in vivo weight-bearing conditions. However, patellar rotation in the coronal plane was weakly correlated with the trochlear geometry.

Late Repair of an Osteochondral Fracture of the Patella

Acute patellar dislocations are a common injury in young patients. Osteochondral fractures are commonly associated with this injury, frequently necessitating surgical treatment. This article presents a case of a 23-year-old woman who sustained a large osteochondral fracture of the medial facet of the patella during a first-time acute patellar dislocation. The patient was lost to follow-up; consequently, surgical treatment was not performed until 8 weeks after injury. Diagnostic arthroscopy demonstrated a large osteochondral fragment in the suprapatellar pouch and a defect on the medial facet of the patella with early fibrocartilage growth. Using an open approach, the osteochondral fracture was fixed with headless screws buried beneath the cartilage. After fracture fixation, continued lateral subluxation of the patella was present; therefore, to improve patellar tracking and protect our fracture fixation, a Fulkerson tibial tubercle osteotomy (including a lateral release) and a medial patellofemoral ligament repair were performed. At the conclusion of the surgery, we had achieved rigid fixation of the fracture and normalized patellofemoral tracking.At 1 year post-injury, the patient has achieved union of her patellar osteochondral fracture and tibial tubercle osteotomy. She has full range of motion and minimal anterior knee pain and has not experienced further episodes of patellar instability. Even in patients who present in a delayed fashion, consideration should be given to the repair of patellar osteochondral fractures and, if necessary, realignment of the extensor mechanism.

Total Knee Arthroplasty Combined With Medial Patellofemoral Ligament Reconstruction for Osteoarthritic Knee With Preoperative Valgus Deformity and Chronic Patellar Dislocation

We report a challenging case of a 44-year-old woman who had osteoarthritis in the lateral compartment of her right knee with severe valgus deformity and chronic lateral patellar dislocation. Total knee arthroplasty was performed for the knee. However, persistent patellar dislocation remained during the surgery; and therefore, medial patellofemoral ligament (MPFL) reconstruction was additionally performed at the time of the surgery. Stable patellar tracking was obtained after the MFPL reconstruction; and during the 2-year follow-up, her knee functioned well, and no recurrent patellar dislocation was observed. This clinical case indicates the usefulness of MPFL reconstruction for obtaining stable patellar tracking during total knee arthroplasty when a tendency for lateral patellar dislocation remains.

Are Current Total Knee Arthroplasty Implants Designed to Restore Normal Trochlear Groove Anatomy?

Biomechanical studies have shown that external rotation of the femoral TKA component improves patellar tracking but does not restore it to physiologic values. We hypothesized that this could be due to differences in the trochlear groove geometry of TKA and normal knees. This was investigated via a virtual TKA procedure that mounted femoral components on to 3-dimensional models of healthy femurs, followed by measurement of the trochlear geometry before and after the simulated TKA. The results showed that (1) external rotation of the component brought the trochlear groove closer to normal anatomy than no external rotation; (2) however, even with external rotation, the trochlear anatomy was only partially restored to normal. Further work is needed to determine implications for patellofemoral complications observed with current TKA designs.

Optimizing patellofemoral tracking during total knee arthroplasty.

Fifty-seven patients who underwent 65 primary TKAs between 1993-1994 were retrospectively studied to identify the technical challenges and pitfalls associated with patellar resurfacing and to improve patellar tracking during total knee arthroplasty (TKA). Average patient age was 69 years. All surgeries were performed by a single surgeon (J.N.I), and the same prosthesis was used in all patients. Intraoperatively, attention was paid to avoid femoral and tibial component malrotation and prevent overstuffing of the patellofemoral joint. Preoperative limb alignment was varus in 42 knees, neutral in 6 knees, and valgus in 17 knees. Average pre-resection patellar thickness measured 23.8 mm and post-resection thickness averaged 21.5 mm. No patella-prosthesis composite was thicker than the native patella. Two (3%) knees required a formal lateral release to improve patellar tracking at surgery. Average follow-up for 53 patients (61 knees) was 5 years. At latest follow-up, 4 (6%) patients reported mild anterior knee pain, 5 (7%) patients reported pain with stairs, and 2 (3%) patients had knee crepitus without pain. No dislocations or recurrent subluxations occurred. No patient required revision surgery for patellofemoral complication. Awareness of the anatomic variability, attention to component rotation, and restoration of the normal patellar height improves patellar tracking and minimizes patellofemoral instability following TKA.

The sulcus deepening trochleoplasty—the Lyon’s procedure

Sulcus deepening trochleoplasty is a technically demanding procedure with precise indications: high grade trochlear dysplasia with patellar instability and/or abnormal tracking. The main goal is to decrease the prominence of the trochlea and to create a new groove with normal depth, thus optimising patellar tracking. Associated abnormalities should be specifically treated. Recurrence of instability is very rare after this procedure and is more likely to result from missed associated abnormalities. Although results seem very good in terms of instability, further evidence is still needed since the groups of patients in the published series are heterogeneous. Trochleoplasty is not indicated for patellofemoral arthritis or pain. As any surgical procedure, sulcus deepening trochleoplasty is liable to complications.

Early results of total knee arthroplasty performed through the midvastus approach

The aim of this study was to evaluate the early results of total knee arthroplasty (TKA) performed through the midvastus approach. This retrospective study included 48 knees of 42 patients (29 females, 13 males; mean age 69 years; range 54 to 82 years) who underwent TKA for grade 4 knee osteoarthritis. All TKA operations were performed by the same orthopedic surgeon through the midvastus approach. Preoperatively, 40 patients (95.2%) had primary osteoarthritis, and two patients (4.8%) had rheumatoid arthritis. In all cases, a posterior stabilized cemented prosthesis with a fixed insert was used. Patellar resurfacing was performed in seven knees (14.6%). All the knees were rated according to the Knee Society knee and function scores before surgery and at the final follow-up. Postoperative radiographic evaluations were performed on anteroposterior and lateral radiographs according to the Knee Society TKA Roentgenographic Evaluation and Scoring System. The mean follow-up period was 26 months (range 12 to 49 months). The mean knee score significantly improved from 49.0+/-9.3 preoperatively to 87.5+/-9.9 postoperatively (p=0.000). The corresponding increase in the knee function score was from 48.8+/-9.9 to 79.6+/-14.0 (p=0.000). The mean increases in the knee and function scores were 38.5 and 30.8 points, respectively. The knee and function scores were excellent or good in 46 knees (95.8%) and 42 knees (87.5%), respectively. The mean knee flexion significantly increased by 28.6 degrees , from 84.3+/-14.7 degrees preoperatively to 112.9+/-11.9 degrees postoperatively (p=0.000). Among patients with bilateral osteoarthritis, the knee function scores were significantly higher in patients who had undergone bilateral versus unilateral TKA (90.0+/-11.5 and 78.8+/-10.8, respectively; p=0.007). None of the patients had patellar tracking abnormality intraoperatively; thus, there was no need for lateral retinacular release. Postoperative clinical and radiographic assessments showed no signs of instability or loosing. Clinical and radiographic loosening of the patella and osteolysis were not observed in patients who had undergone patellar replacement. No changes were observed in the tracking and position of the protheses. Neurovascular injury did not occur. One patient who developed early infection of the knee that required a two-stage revision was assessed as failure. In our study, lateral retinacular release was not needed due to achievement of proper patellar tracking in TKA operations with the midvastus approach, and satisfactory clinical and radiographic results were obtained.

CSM 2010 Orthopaedic Section Platform Presentations (Abstracts OPL1-OPL67)

CSM 2010 Orthopaedic Section Platform Presentations (Abstracts OPL1-OPL67)

Clinical Value of "The Single Stitch Method" in Intraoperative Assessment of Patellar Tracking in Total Knee Arthroplasty

Clinical Value of "The Single Stitch Method" in Intraoperative Assessment of Patellar Tracking in Total Knee Arthroplasty

Measuring Patellofemoral Forces and Pressures in a Simulated Operating Room Environment

The purpose of this study was to use a validated capacitive pressure (Novel Electronics, Inc, St Paul, Minn) in the measurement and distribution of patellofemoral forces and pressures during simulated operative procedures. Six fresh frozen cadaver knees were evaluated through a range of motion and observations recorded in native knees (NKNP) with sequential resurfacing of tibiofemoral (RKNP) and patellofemoral (RKRP) articulations with standard and gender (GKRP) components. Significant lateral-medial maximum force differentials were observed for all conditions. Significant lateral-medial peak pressure differentials were observed in RKNP and RKRP. A significant decrease in lateral maximum force from RKRP to GKRP ( P = .01) was observed. Significant increases in lateral peak were seen from NKNP to RKNP ( P = .04) and RKNP to RKRP ( P = .047), whereas a significant decrease was seen from RKRP to GKRP ( P < .01). Achieving a quantitative intraoperative assessment of patellar tracking and soft tissue balancing may offer benefits in terms of intraoperative decision making. This is the first reported study to simulate quantitative, intraoperative assessments of patellofemoral pressure and force.

Differences in patellofemoral contact mechanics associated with patellofemoral pain syndrome

Patellofemoral pain syndrome (PFPS) is a disorder of the patellofemoral (PF) joint in which abnormal tracking is often cited as a factor in pain development. PF tracking is partially dependent on passive stabilizers (ex: PF geometry). Relations amongst PFPS, PF tracking, and contact mechanics are poorly understood. In-vivo investigation of passive PF joint stabilizers including PF tracking, contact mechanics, cartilage thickness, and patellar shape will allow structural characterization of the PF joint and may highlight differences associated with PFPS. This study examined the role that passive stabilizers play in PFPS ( n=10) versus healthy subjects ( n=10). PF tracking (contact area centroid migration), cartilage thickness, shape, congruence, and contact patterns were quantified using magnetic resonance imaging during isometric loading at 15°, 30°, and 45° of knee flexion. Distinct relationships were identified between patellar shape and tracking and contact, particularly at low flexion (15–30°). Healthy subjects exhibited distinct PF tracking and contact patterns related to Type I patella shape (80%) with increasing total contact area ( p<0.001) and proximal centroid migration (15–30° p=0.012; 30–45° p<0.001) for increasing knee angles. PFPS subjects deviated from these patterns at low flexion, demonstrating higher total contact area than healthy subjects ( p=0.046 at 15°), lack of proximal centroid migration (15–30°), and more Type II (30%) and III (20%) patella shapes. This study highlights a new finding that patellar shape combined with low degrees of flexion (15–30°) may be important to consider, as this is where PFPS tracking and contact patterns deviate from healthy.

In vivo patellar tracking induced by individual quadriceps components in individuals with patellofemoral pain

Patellofemoral pain is a common knee disorder with a multi-factorial etiology related to abnormal patellar tracking. Our hypothesis was that the pattern of three-dimensional rotation and translation of the patella induced by selective activation of individual quadriceps components would differ between subjects with patellofemoral pain and healthy subjects. Nine female subjects with patellofemoral pain and seven healthy female subjects underwent electrical stimulation to selectively activate individual quadriceps components (vastus medialis obliquus, VMO; vastus medialis lateralis, VML; vastus lateralis, VL) with the knee at 0° and 20° flexion, while three-dimensional patellar tracking was recorded. Normalized direction of rotation and direction of translation characterized the relative amplitudes of each component of patellar movement. VMO activation in patellofemoral pain caused greater medial patellar rotation (distal patellar pole rotates medially in frontal plane) at both knee positions ( p<0.01), and both VMO and VML activation caused increased anterior patellar translation ( p<0.001) in patellofemoral pain compared to healthy subjects at 20° knee flexion. VL activation caused more lateral patellar translation ( p<0.001) in patellofemoral pain compared to healthy subjects. In healthy subjects the 3-D mechanical action of the VMO is actively modulated with knee flexion angle while such modulation was not observed in PFP subjects. This could be due to anatomical differences in the VMO insertion on the patella and medial quadriceps weakness. Quantitative evaluation of the influence of individual quadriceps components on patellar tracking will aid understanding of the knee extensor mechanism and provide insight into the etiology of patellofemoral pain.

In vitro analysis of patellar kinematics: validation of an opto-electronic cinematic analysis protocol

Opto-electronic cinematic analysis has already proven useful in the investigation of patients with a knee replacement; however, neither patellar tracking nor the various positional parameters relevant to instability such as patellar tilt and/or patellar shift have ever been specifically evaluated using this type of system. The aim of this research was to validate the relevance of this type of cinematic analysis in order to use it in the evaluation of the main factors underlying patellar instability. Six fresh-frozen anatomical specimens were studied. The data were acquired using the Motion Analysis system. Statistical analysis reveals a good reproducibility of measurements. Our protocol based on an opto-electronic acquisition system has an accuracy of 0.23 mm for shift and of 0.4 degrees for rotation, which is calculated by integrating the various experimental parameters and instrumental features specific to the Motion Analysis system. The results are consistent with published results which further attests to the validity and the efficacy of the protocol and encourages us that this protocol is suitable for the in vitro study of patellar kinematics.