Objective Patellar Instability Research Articles

Framing Patellar Instability: From Diagnosis to the Treatment of the First Episode.

The patellofemoral joint (PFJ) is a complex articulation between the patella and the femur which is involved in the extensor mechanism of the knee. Patellofemoral disorders can be classified into objective patellar instability, potential patellar instability, and patellofemoral pain syndrome. Anatomical factors such as trochlear dysplasia, patella alta, and the tibial tuberosity-trochlear groove (TT-TG) distance contribute to instability. Patellofemoral instability can result in various types of dislocations, and the frequency of dislocation can be categorized as recurrent, habitual, or permanent. Primary patellar dislocation requires diagnostic framing, including physical examination and imaging. Magnetic resonance imaging (MRI) is essential for assessing the extent of damage, such as bone bruises, osteochondral fractures, and medial patellofemoral ligament (MPFL) rupture. Treatment options for primary dislocation include urgent surgery for osteochondral fragments or conservative treatment for cases without lesions. Follow-up after treatment involves imaging screening and assessing principal and secondary factors of instability. Detecting and addressing these factors is crucial for preventing recurrent dislocations and optimizing patient outcomes.

Patellar medial closing-wedge osteotomy in patello-femoral instability: Indications and outcomes

BackgroundPatellofemoral (PF) instability is a syndrome involving several factors and conditions. Trochlear dysplasia (TD) has been shown to be the feature most frequently diagnosed in patients with OPI (Objective Patellar Instability). Even the patella might have an altered shape. Articulating during growth with an abnormal trochlea might lead the patellar posterior surface to modify accordingly, becoming congruent with the trochlear shape. A mismatch between the two articulating surfaces has a role in patellofemoral dislocations.Rarely and in case of a highly dysplastic patella, reshaping only the trochlear groove might lead subsequently to an incongruence between the two bones.When isolated sulcus-deepening trochleoplasty does not restore a congruent patellofemoral tracking tested perioperatively, further surgical procedures might be required. MethodsA medial closing wedge patellar osteotomy (MCWPO) added to sulcus deepening trochleoplasty should be performed to create a congruent patellofemoral joint.Indications for this procedure are Wiberg type III or IV patella with an intraoperative abnormal patellar tracking after the sulcus deepening trochleoplasty procedure has been concluded. ResultsFrom January 2012 to August 2020, 21 (6 right and 15 left knees) sulcus deepening trochleoplasties with a concomitant medial closing wedge patellar osteotomy have been performed. The mean follow up was 35,25 months (ranging from 10 to 60 months). The average Kujala, IKDC and Lysholm score were respectively 70,14 ± 15,51; 55,75 ± 7,12 and 77,12 ± 14,80. No further patellar dislocation has been assessed in those patients during follow up. ConclusionThis technique has shown good and promising clinical outcomes and should be considered when treating patients with a still unsatistactory patellofemoral tracking after the sulcus deepening trochleoplasty has been performed due to a patella-trochlea shape mismatch.

Bioabsorbable magnesium screw fixation for tibial tubercle osteotomy; a preliminary study.

Background and aim:Metallic screws are commonly used to fix tibial tubercle osteotomies (TTO). However, hardware removal late after osteotomy union is one of the most common causes of reoperation following TTOs. The use of bioabsorbable screws may eliminate secondary surgeries, but there is no study on their use in this indication. The purpose of this retrospective study was to evaluate the safety and efficacy of bioabsorbable magnesium (Alloy: MgYREZr) screws in tibial tubercle osteotomy (TTO) fixation.Methods:Ten consecutive patients with objective patellar instability who underwent distal realignment procedure using Fulkerson TTO were retrospectively reviewed. The osteotomy was secured with two parallel 4.8 mm magnesium screws in all patients. Kujala score and Lysholm knee score were used to assess the functional outcomes before and after the operation. During the follow-up, the union of the osteotomy, displacement, and other imaging findings were evaluated with serial knee radiographs.Results:There were five male and five female patients with a mean age of 23.4±9.2 years (range, 15–45). The mean follow-up duration was 11.5±3.2 months (range,6–17 months). The osteotomy united in all cases at an average of 3 months. No infection or wound healing problems were seen. A significant increase in Kujala (p:.005) and Lysholm knee scores (p:.005) were recorded in all patients.Conclusion:Despite a limited number of patients were reviewed, the findings support that bioabsorbable magnesium screws can be safely used as an alternative fixation technique in TTO. Furthermore, it provides the advantage of eliminating the need for implant removal. (www.actabiomedica.it)

Anatomic medial patellofemoral ligament (MPFL) reconstruction with and without tibial tuberosity osteotomy for objective patellar instability

PurposeThe aim of this study was to evaluate the clinical outcomes of patients treated with anatomic medial patellofemoral ligament (MPFL) reconstruction with and without tibial tuberosity osteotomy (TTO). Correlations between patient's age, gender, pre-injury physical activity and the achieved results were investigated as secondary endpoints.MethodsAn observational retrospective study with prospective collected data was performed. Inclusion criteria were: treatment with anatomic MPFL reconstruction with gracilis tendon according to Schӧttle’s technique performed between 2011 and 2017; associated TTO as unique accessory procedure; skeletal joint maturity; a minimum follow-up of 12 months after surgery. Clinical outcomes were assessed with the Kujala, Lysholm and Tegner scores.ResultsForty patients (42 knees) were included, 64% of them underwent TTO. The Kujala score significantly improved from 47.4 ± 17.6 preoperatively to 89.4 ± 13.6 postoperatively (p < 0.01). The average Lysholm score was 45.6 ± 20.5 preoperatively: it showed a significant increase to 89.8 ± 12.8 postoperatively (p < 0.01). Pre-injury mean Tegner was 5.9 ± 1.8, while it dropped to 3.0 ± 1.6 after injury. After surgery, Tegner resulted 4.9 ± 1.6. Forty-three percent of patients regained the pre-injury sport activity level. Redislocation rate was 2.4%.ConclusionAnatomic MPFL reconstruction allows excellent patellar stability recovery, knee functionality improvement, return to Activities of Daily Living and a low redislocation rate. Better results were achieved in younger (under 30 years old) and higher sports activity-level subjects. The TTO association provided clinical results comparable to isolated MPFL reconstructions, suggesting that the two procedures can be safely accomplished together without affecting the positive outcomes.Level of evidenceLevel IV.

Management of objective patellar instabilities at the University Hospital Center Sylvanus Olympio of Lome, Togo

Introductionl´instabilité patellaire est une affection rare, multifactorielle et dont la prise en charge est complexe. Le but de notre étude était de décrire les cas d´instabilités patellaires, puis d´évaluer les résultats du traitement dans un pays à faible revenu.Méthodesl´étude s´est déroulée de mars 2013 à février 2018. Elle a porté sur huit patients qui avaient un âge supérieur à 15 ans et qui avaient été traités chirurgicalement pour instabilité patellaire objective. La fonction du genou avant et après le traitement chirurgical a été appréciée par le score IKDC.Résultatsl´âge moyen lors de la chirurgie était de 28,5 ans et le sexe féminin prédominait avec six cas. La dysplasie de la trochlée a été le principal facteur étiologique retrouvé chez sept patients. Dans quatre cas cette dysplasie était associée à la hauteur de la patella avec l´index de Caton moyen de 1,4. Dans cinq cas, il a été réalisé la section du retinaculum patellaire latéral associée à la transposition de la TTA et à la plastie d´Insall. L´évaluation fonctionnelle du traitement a été satisfaisante, avec un score IKDC moyen de 91,3%.Conclusionles instabilités patellaires sont rares. Leur prise en charge est retardée dans nos pays en voie de développement, mais les résultats sont bons si les protocoles sont adaptés.

Patellar instability can be classified into four types based on patellar movement with knee flexion: a three-dimensional computer model analysis

ObjectivePatellar instability (PI) represents various underlying pathologies, including patellar malalignment. Continuous patellar alignment develops to patellar tracking and is regarded as the end product of combined predisposing factors. We quantitatively investigated the inhomogeneity of patellar tracking in PI.MethodsSixty knees of 56 patients with PI and 15 knees of 10 healthy volunteers (HVs) were studied. Three-dimensional (3D) computer models were created based on MRIs at 10° intervals over 0°–50° of flexion, and patellar tracking was quantitatively analysed using patellar 3D shift. Classification was performed according to the maximum 3D shift (max-shift), indicating the extent of lateral deviation, and the change of 3D shift from 0° to 50° (change0–50), indicating movement direction. First, the cut-off value (COV) of the max-shift was defined based on the data from HVs. When a value was greater than the COV, it was defined as a major subluxation, and when the value was smaller it was defined as a minor subluxation. Next, the two COVs of change0–50 were similarly defined. When a value was greater than the upper COV, it was defined as a major-lateral type, laterally moving the patella with flexion, and when smaller than the lower COV it was defined as a major-medial type, medially moving the patella with flexion. When a value fell between the two COVs, it was defined as a major-straight type.ResultsFifty-three patellae (88%) with values larger than the COV of the max-shift (mean +1 SD of HV) were defined as major subluxations and seven (12%) showing smaller values as minor subluxations. Among the major subluxations, 25 (42%) showing a smaller value than the lower COV of change0–50 (mean –2 SD of HV) were defined as major-medial type, while 7 (12%) showing a larger value than the upper COV of change0–50 (mean +2 SD) were defined as major-lateral type. Twenty-one (35%) were defined as major-straight type. No further analysis was performed on the seven minor subluxations (the minor type).ConclusionPI was quantitatively classified into four types according to the extent of lateral deviation and the movement direction of the patellae with flexion, showing inhomogeneity of patellar tracking.

A combined procedure with Bereiter-type trochleoplasty leads to a stable patellofemoral joint at 5-year follow-up.

Trochlear dysplasia is a major risk factor predisposing to patellar instability and has been reported to occur in up to 85% of patients with recurrent patellar dislocation. Different operative techniques have been described to correct trochlear dysplasia, including the Bereiter technique, in which subchondral bone is removed and the cartilage can be compressed into a U-shaped groove. The hypothesis was that after a Bereiter-type trochleoplasty combined with medialisation of the tibial tubercle and MPFL reconstruction, patellar pain and instability decreased and anatomic reconstruction can be seen radiographically after 5-year follow-up. Between 2004 and 2011, a combined procedure including Bereiter-type trochleoplasty was performed on 21 consecutively included patients (22 knees) with objective patellar instability and severe trochlear dysplasia. Instability and pain were assessed preoperatively and 3, 6, 12, 24 and 60months postoperatively with the visual analogue scale (VAS) for pain and instability, Kujala, International Knee Documentation Committee Subjective Knee Evaluation (IKDC SKE) and Short Form Health Survey (SF-36). Pre- and postoperatively, a true lateral radiograph was made to investigate the presence of the crossing sign and to measure the trochlear bump and trochlear depth, as well as a sunrise patella view to measure the sulcus angle. VAS pain and instability, Kujala and IKDC SKE improved significantly 5 years after trochleoplasty (p < 0.05). SF-36 showed no significant improvement. None of the patients reported patellar dislocations postoperatively. Sport activities remained limited. Postoperative radiographs showed no crossing sign. There was a significant increase in trochlear depth (p < 0.0001) and also a significant decrease in trochlear bump and sulcus angle (both p < 0.0001). A combined procedure consisting of Bereiter-type trochleoplasty, medialisation of the tibial tubercle and MPFL reconstruction in patients with objective patellar instability and severe trochlear dysplasia resulted in a clear decrease of pain and instability. Radiological assessment showed anatomical reconstruction. Nevertheless, residual symptoms remain and the possibility of future cartilage damage is uncertain. IV.

Distalization and Medialization of Tibial Tuberosity for the Treatment of Potential Patellar Instability with Patella Alta

Purpose The aim of the study was to test the distalization and medialization of the tibial tuberosity (DMTT) for the treatment of patellar instability associated with patella alta, focusing on residual instability and pain. Methods Twenty-four consecutive patients (26 knees) suffering from patellofemoral instability and patella alta were treated by DMTT. Two groups were identified, which differed for documented history of frank patella dislocation. The groups were named objective patellar instability (OPI) (history of dislocation) and potential patella instability (PPI) (no dislocation). Outcome was measured with visual analogue scale (VAS), Kujala score, and Tegner score. Comparison between groups was performed using Student's t -test, Wilcoxon rank score, and Fisher's exact test (significance at p < 0.05). Results At 50 ± 18 and 41 ± 18 months of follow-up, respectively, both PPI and OPI groups obtained a significant pain reduction and functional improvement. The PPI group showed a significant decrease of the subjective instability. No procedure-related complications were reported. Conclusion This study suggests that DMTT is a viable option for PPI patients with patella alta. The outcome was comparable between PPI and OPI cases; however, decrease in subjective instability was significantly greater in PPI patients. Level of Evidence Level III, retrospective comparative study.

Surgical Treatment of Objective Patellar Instability: Long-Term Results.

Purpose To evaluate the long-term results of classical “à la carte” surgical treatment of objective patellar instability as proposed by Dejour in 1987. Methods A multicentric retrospective study was conducted evaluating patients that underwent surgical procedure with a 10-year minimum follow-up (mean 12.7; range, 10–15). Surgical procedures were medial transfer of the tibial tubercle transfer according to Elmslie and Trillat et al in 38 cases, plasty of the vastus medialis obliquus according to Insall in 15 cases, open lateral retinacular release in 13 cases, capsuloplasty in 3 cases, and trochleoplasty in 1 case. Different combinations of surgical procedures were adopted according to the pathological features. Subjective outcome was assessed with the visual analog scale (VAS), Kujala score, subjective International Knee Documentation Committee (IKDC) score, Tegner score, and Crosby and Insall scale. Radiographic exams were used to assess the patellar tilt by the Laurin's angle and patellofemoral osteoarthritis (OA) according to the Iwano radiological OA scale. Results Forty patients were evaluated. Subjectively, 60% of patients achieved a result judged good, 34% sufficient, and 6% poor. There were only two cases of recurrence of instability. Mean score results were Kujala score 73.4 ± 9.9 (range, 55–95), VAS 4.5 ± 1.2 (range, 1–6), IKDC 64.8 ± 7.9 (range, 51–88), and Tegner score 4. Only nine patients returned to sports activities). Ten patients developed a grade I patellofemoral OA, 8 patients a grade II, and 22 patients a grade III. Average patellar tilt was 10° ± 3.9°. Conclusion This retrospective study showed that the traditional surgical procedure was successful for the treatment of patellar instability, but it did not prevent symptomatic patellofemoral OA. Level of Evidence Level IV, retrospective case series.

Anatomic Double-Bundle Medial Patellofemoral Ligament Reconstruction with Autologous Semitendinosus: Aperture Fixation Both at the Femur and the Patella.

Medial patellofemoral ligament (MPFL) represents the main restraint against lateral patellar displacement. The MPFL insertion at the patella is up to 30 mm wide and is located along the upper half of the medial patellar rim. The femoral insertion of the MPFL is approximately 10 mm distal to the apex of the adductor tubercle and 16 mm proximal to the medial epicondyle. Since most of the patients suffer from MPFL rupture just after the first patellar dislocation, MPFL reconstruction results necessarily in all cases of chronic objective patellar instability to reestablish the primary passive patellofemoral stabilizer. Over time, different techniques of MPFL reconstruction have been proposed with promising results in terms of patient satisfaction and redislocation rate. However, each of these techniques may present peculiar problems and/or complications. An anatomic double-bundle MPFL reconstruction through an aperture fixation both at the femur and at the patella is here presented. The anatomic double-bundle MPFL reconstruction could allow recreating the fan-shape and biomechanics of original MPFL, whereas aperture fixation could provide a strong and safe fixation without risk of loosening or slackening of the graft.

Treatment of the Objective Patellofemoral Instability

Objectives:The aim of this study is to show the different surgical procedures for treating the objective patellar instability, including the different tibial tubercle osteotomies and the sulcus deepening trochleoplasty.Methods:This study analyzed the Caton-Deschamps index used for assessment of patellar height, the distance from the tibial tubercle to the troclear groove (TT-TG) on CT Scan in the axial view, and the different trochlear and patellar morphotypes. This study included 19 knees (19 patients) treated in an objective and documented patellofemoral instability.Results:We have had good results with both the transfer of the tibial tuberosity as the trochleoplasty. A reconstruction of the medial patellofemoral ligament was performed in both procedures. Recurrence of instability is very rare after these procedures and this is more likely to result from missed associated abnormalities.Conslusion:Accurate preoperative planning of the patellar height and determining the location of the tibial tubercle and the trochlear and patellar morphotypes for satisfactory results are required. However, as with any surgical procedure, both tibial tubercle osteotomy and the sulcus deepening trochleoplasty are susceptible of complications.

Medial patellofemoral ligament reconstruction: Clinical and radiographic results in a series of 90 cases

IntroductionAmong the numerous techniques available, medial patellofemoral ligament (MPFL) reconstruction is increasingly used for the surgical treatment of objective patellar instability. The main objective of the present study was to assess efficacy in preventing recurrence of patellar dislocation and in correcting radiographic patellar tilt. The study hypothesis was that MPFL reconstruction, isolated or with associated bone surgery, by restoring “favorable” graft anisometry, provides a good trade-off between patellar stability and absence of postoperative stiffness. Materials and methodsEighty-seven patients (90 reconstructions) presenting with objective patellar instability were prospectively included. The standardized procedure comprised MPFL reconstruction using the gracilis tendon. Femoral fixation used an interference screw in a blind tunnel between the adductor magnus tubercle and the medial epicondyle; patellar fixation used 2 anchors. Complementary distal bone graft was associated in 21 patients due to a preoperative tibial tubercle-trochlear groove (TT-TG) distance exceeding 20mm or to patella alta. Functional IKDC and Kujala scores and radiographic measurement of patellar tilt and femoral tunnel position were assessed preoperatively and at end of follow-up. ResultsMean follow-up was 24.3months (range, 6–49months). Three patients showed recurrence of patellar dislocation. Mean Kujala score rose from 53.88 preoperatively to 86.24 postoperatively, and mean real IKDC score from 45.15 to 73.92 (P<0.001). Patellar tilt decreased significantly between pre- and postoperative X-ray (P<0.001). DiscussionMPFL gracilis reconstruction provides good clinical results and good radiologic correction of patellar tilt, making it a technique of choice in the treatment of objective patellar instability. Level of evidenceLevel IV. Retrospective case series study.

Recovery of gait pattern after medial patellofemoral ligament reconstruction for objective patellar instability.

Gait pattern alterations were previously reported in association with objective patellar instability (OPI). Gait pattern comparison between a series of patients having undergone medial patellofemoral ligament (MPFL) reconstruction and a sample of control subjects. Thirty patients at 6 months postoperatively after MPFL reconstruction and thirty control subjects were enrolled in the study for a clinical and biomechanical assessment including gait analysis at three selected walking rates using the GAITRite(®) system. The mean raw IKDC score was 73 (± 19), and the mean Kujala knee function was 84 (± 17.5). The study of gait did not demonstrate any significant difference between the two groups at a normal and fast walking rate. At a 10 km/h running speed, the single-support phase was significantly shortened by a mean 2.33% (p < 0.05), the swing phase by a mean 2.64% (p < 0.05) and the double-support phase by a mean 3.49% (p < 0.05) on the operated side. MPFL reconstruction reported good midterm functional and clinical results in the management of OPI. At 6 months postoperatively, the patient gait pattern was similar to that observed in healthy subjects at a normal and fast walking speed. However, our study revealed persistent gait abnormalities at a 10 km/h running speed. These gait alterations seemed to be related to the ligament reconstruction in itself due to the higher strain applied on the reconstructed MPFL during running cycle (10 km/h). Level of evidence IV.

Axial MRI index of patellar engagement: A new method to assess patellar instability

The aim of this study was to define a new index to measure lateral patellar displacement (LPD) using nuclear magnetic resonance imaging (MRI), an axial index of engagement of the patella (AEI) obtained from two different axial MRI views then to validate its use in a prospective series of patients presenting an objective patellar instability (OPI). One hundred and thirty-five patients with OPI and no history of surgery of the patella were included in a prospective study organized by the French Society of Arthroscopy performed between June 2010 and August 2012. All patients underwent axial and sagittal MRI. The AEI was obtained by projecting predefined patellar and trochlear landmarks (cartilaginous landmarks) on 2 different axial MRI views (one trochlear and one patellar). The results were compared with a series of controls (n=45). The preoperative AEI of the patella was 0.94 ± 0.09 for the control group and 0.84 ± 0.16 for OPI group (P=0.000016). The AEI could be obtained in 100% of the cases if it was measured on 2 MRI views while it could not be measured in 38.5% of the cases if the measurement was only obtained from one MRI view or whenever the widest part of the patella was not across from the femoral trochlea. The AEI did not significantly depend on dysplasia or the presence of a supratrochlear spur. The lowest AIE values were associated with trochlear dysplasia with a supratrochlear spur (P=0.0023) and a more prominent trochlea (P=0.0016). The AEI was correlated with patellar tilt (P<0.000001) and TT-TG on MRI (P<0.000001). AEI is a new index to measure LPD. It can be obtained in all cases because it is obtained from two different MRI views. The normal value is close to 1. It can be used to measure patellar instability on the axial plane in patients with OPI, especially in the most severe cases.

Patellar shape can be a predisposing factor in patellar instability

Predisposing factors to objective patellar instability include trochlear dysplasia, patella alta, patellar tilt and elevated tibial tuberosity-femoral groove distance. The shape of the patella is classically not considered a predisposing factor. Anomalies of dynamic and static factors, including excessive patellar height, tibial tubercle lateralisation or trochlear dysplasia, may influence the development of the patella. One hundred and five patients (140 knees) with objective patellar instability were retrospectively reviewed to identify a possible association between the above-mentioned predisposing factors and patellar shape. All patients were evaluated with static and dynamic CT scans, and plain lateral and antero-posterior radiographs, and skyline patellar views. Evidence of a significant association emerged between patellar shape and patellar tilt in static (r(s) = 0.20, P = 0.019) or dynamic conditions (r(s) = 0.18, P = 0.031) and a significant association between Wiberg patellar shape type C and trochlear dysplasia grade 3 (χ(2) = 4.5, P = 0.035). Also, we found a significant association between trochlear dysplasia stage 3 and tibial tuberosity-trochlear groove (TT-TG) and patellar tilt relaxed (P < 0.01 and P < 0.05, respectively). There is an association between patellar shape and patellar tilt. Increased lateral stresses may produce a Wiberg type C patella, with a hypoplastic medial facet and a more developed lateral facet. Unbalance between dynamic medial and lateral stabilisers may act as an additional factor. A rehabilitation program aiming to reduce this unbalance may decrease the incidence of type C patella in young patients.

The effect of trochleoplasty on patellar stability and kinematics

Objective patellar instability has been correlated with dysplasia of the femoral trochlea. This in vitro study tested the hypothesis that trochleoplasty would increase patellar stability and normalise the kinematics of a knee with a dysplastic trochlea. Six fresh-frozen knees were loaded via the heads of the quadriceps. The patella was displaced 10 mm laterally and the displacing force was measured from 0 degrees to 90 degrees of flexion. Patellar tracking was measured from 0 degrees to 130 degrees of knee flexion using magnetic sensors. These tests were repeated after raising the central anterior trochlea to simulate dysplasia, and repeated again after performing a trochleoplasty on each specimen. The simulated dysplasia significantly reduced stability from that of the normal knee (p < 0.001). Trochleoplasty significantly increased the stability (p < 0.001), so that it did not then differ significantly from the normal knee (p = 0.244). There were small but statistically significant changes in patellar tracking (p< 0.001). This study has provided objective biomechanical data to support the use of trochleoplasty in the treatment of patellar instability associated with femoral trochlear dysplasia.

Instabilités de la rotule: histoire, étiologie et indications pour le traitement. Le menu à la carte de 2008

Patellar instability is defined by clinical and radiological criteria. There are three populations, known as Objective Patellar Instability, Potential Patellar Instability, Patellar Painful Syndrome. Surgical treatment is aimed at restoring the congruence of the patello-femoral articulation and correcting extensor mechanism malalignment, to prevent recurrence of dislocation. The standard soft-tissue procedures are lateral release and vastus medialis advancement and patello-femoral medial 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 morphological 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.

A modified tibial tubercle osteotomy for patellar maltracking

An abnormal lateral position of the tibial tuberosity causes distal malalignment of the extensor mechanism of the knee and can lead to lateral tracking of the patella causing anterior knee pain or objective patellar instability, characterised by recurrent dislocation. Computer tomography is used for a precise pre-operative assessment of the tibial tubercle-trochlear groove distance. A distance of more than 15 mm is considered to be pathological and an indication for surgery in symptomatic patients. In a prospective study we performed a subtle transfer of the tibial tuberosity according to the information gained from the pre-operative CT scan. This method was applied to two groups of patients, those with painful lateral tracking of the patella, and those with objective patellar instability. We evaluated the clinical results in 30 patients in each group. The outcome was documented at 3, 12 and 24 months using the Lysholm scale, the Kujala score, and a visual analogue pain score. Post-operatively, all but one patient in the instability group who had a patellar dislocation requiring further surgery reported good improvement with no further subluxation or dislocation. All patients in both groups had a marked improvement in pain and functional score. Two patients sustained a tibial fracture six and seven weeks after surgery. One patient suffered a per-operative fracture of the tibial tubercle which later required further fixation. If carefully performed, this type of transfer of the tibial tubercle appears to be a satisfactory technique for the treatment of patients with an increased tibial tubercle-trochlear groove distance and who present with symptoms related to lateral maltracking of the patella.

Objective patellar instability: MR-based quantitative assessment of potentially associated anatomical features

To evaluate and compare the diagnostic utility of multiple quantitative parameters as measured on knee magnetic resonance (MR) examinations of patients suffering objective patellar instability (OPI). We performed a retrospective evaluation of knee MR examinations in a group of 46 patients (59 knees) with clinically proven OPI, and in a control group of 69 patients (71 knees). Multiple quantitative parameters in both groups were statistically evaluated and compared for their association with OPI. OPI patients tend to present shallower trochlear groove (<5 mm), larger Insall-Salvati index (>1.2), shorter patellar nose (<9 mm), smaller morphology ratio (<1.2), and larger patellar tilt (>11 degrees ) than control patients. The best sensitivities were those of the lateral patellar tilt (92.7%), the trochlear groove depth at the roman arch level (85.7%) and the Insall-Salvati index (78%). The best specificities were those of the morphology ratio (86.9%), the patellar nose (84.5%) and the patellar tendon length (84.5%). Shallow trochlear groove may be confidently identified at the roman arch view in OPI patients. Patella alta may be more reliably detected by the Insall-Salvati index in OPI patients. Patellar nose and morphology ratio are very specific indicators of OPI. A short patellar nose (that is to say, a patellar nose ratio of <0.25) has a high association with OPI. Lateral patellar tilt remains the single feature with the highest sensitivity and specificity for identifying OPI patients.

Fulkerson's modified Elmslie-Trillat procedure for objective patellar instability and patellofemoral pain syndrome.

Twenty two knees were either operated for objective patellar instability (Group A: 14 patients) or patellofemoral pain syndrome (Group B: 8 patients) using Fulkerson's modified Elmslie-Trillat procedure. The objective of this retrospective study was to evaluate the results of this method and to detect whether or not there were differences in the outcome comparing the two groups. Twenty knee joints (Group A: 13; group B: 7) were available for clinical and radiographic examination after an overall mean follow-up of 63 months. Duration of pre- and postoperative physical therapy was significantly longer for group B, the activity level increased significantly for these patients and the Q-angle could be corrected significantly in this group comparing pre- and postoperative values. The overall outcome (Turba score) detected no statistically significant difference between the groups, only good and excellent results were obtained. No signs of osteoarthritis were found radiologically. A pathological patellar congruence angle could be corrected significantly by this method. We conclude that Fulkerson's modified Elmslie-Trillat operation is an excellent treatment method with a very low morbidity for patients with patellofemoral malalignment after failed conservative treatment.