Introduction. Patellofemoral instability is one of the most common presentations to a children's orthopaedic clinic. Recurrent patellar dislocations and instability episodes are painful, disabling and increase the risk of irreversible chondral damage. The medial patellofemoral ligament is the primary static stabiliser to prevent lateral dislocation of the patella and is almost always torn or attenuated in these cases. Reconstruction of this ligament is commonly performed using autologous hamstring tendon however there has been some interest recently in use of quadriceps tendon as a graft. Children with patellar instability also present unique challenges due to the small size of the patella and the presence of open growth plates which may require adaptations to the common techniques. Methods. Patients undergoing medial patellofemoral ligament reconstruction using quadriceps tendon autograft were identified using electronic theatre records. Prospectively collected clinical records and imaging findings were reviewed and underlying pathology, additional procedures at time of MPFL reconstruction, current function and need for further revision surgery determined. Results. Between January 2019 and August 2023, 50 MPFL reconstructions were performed in 37 children using partial thickness quadriceps autograft. Patient age at time of surgery ranged from 5 to 17 years (median age 13 years). The technique was utilised for a variety of indications including recurrent traumatic and habitual patellofemoral instability, fixed dislocations, and revision MPFL reconstruction. Conclusion. Partial thickness quadriceps tendon autograft can be used safely to primarily reconstruct the medial patellofemoral ligament in paediatric population, including those children with open growth plates. It also has utility in revision cases following previous failed hamstring MPFL reconstruction. We have noted that the younger the child, the more distal to the physis lies the femoral point of isometricity, rendering this a safe and reproducible treatment in this age group. Use of this technique has increased in our unit as we have observed that patients seem to be satisfied with their clinical and functional outcomes with a low incidence of short- and medium-term complications

The Banff Patellofemoral Instability Instrument 2.0 (BPII 2.0) is a patient-reported disease-specific quality of life (QOL) outcome measure used to assess patients with recurrent lateral patellofemoral instability (LPI) both pre- and post-operatively. The purpose of this study was to compare the BPII 2.0 to four other relevant patient reported outcome measures (PROMs): the Tampa Scale-11 for kinesiophobia (TSK-11), the pain catastrophizing scale (PCS), a general QOL (EQ-5D-5L), and a return to sport index (ACL-RSI). This concurrent validation sought to compare and correlate the BPII 2.0 with these other measures of physical, psychological, and emotional health. The psychological and emotional status of patients can impact recovery and rehabilitation, and therefore a disease-specific PROM may be unable to consistently identify patients who would benefit from interventions encompassing a holistic and person-focused approach in addition to disease-specific treatment. One hundred and ten patients with recurrent lateral patellofemoral instability (LPI) were assessed at a tertiary orthopaedic practice between January and October 2021. Patients were consented into the study and asked to complete five questionnaires: the BPII 2.0, TSK-11, PCS, EQ-5D-5L, and the ACL-RSI at their initial orthopaedic consultation. Descriptive demographic statistics were collected for all patients. A Pearson's r correlation coefficient was employed to examine the relationships between the five PROMs. These analyses were computed using SPSS 28.0 © (IBM Corporation, 2021). One hundred and ten patients with a mean age of 25.7 (SD = 9.8) completed the five PROMs. There were 29 males (26.3%) and 81 females (73.6%) involving 50% symptomatic left knees and 50% symptomatic right knees. The mean age of the first dislocation was 15.4 years (SD = 7.3; 1-6) and the mean BMI was 26.5 (SD = 7.3; range = 12.5-52.6) The results of the Pearson's r correlation coefficient demonstrated that the BPII 2.0 was statistically significantly related to all of the assessed PROM's (p. There was significant correlation evident between the BPII 2.0 and the four other PROMs assessed in this study. The BPII 2.0 does not explicitly measure kinesiophobia or pain catastrophizing, however, the significant statistical relationship of the TSK-11 and PCS to the BPII 2.0 suggests that this information is being captured and reflected. The preliminary results of this concurrent validation suggest that the pre-operative data may offer predictive validity. Future research will explore the ability of the BPII 2.0 to predict patient quality of life following surgery

Patellofemoral instability (PFI) is a common cause of knee pain and disability in the paediatric population. Patella alta, lateralised tibial tubercle, medial patellofemoral ligament (MPFL) deficiency, genu valgum and trochlear dysplasia are well known risk factors. A prospective database was created including patients referred through our physiotherapy pathway following first-time patella dislocation. Patella alta and lateralisation of the tibial tuberosity was treated with a Fulkerson-type tibial tubercle osteotomy(TTO). Medial patellofemoral ligament was reconstructed using quads tendon autograft pull-down technique. A modified Sheffield protocol was used postoperatively allowing weightbearing in a hinged knee brace. Forty patients were identified with 8 patients having bilateral presentations. Male to female ratio was 12:28 with an age range of 4–17 years. Eight patients had congenital PFI, five patients acquired PFI through traumatic patella dislocation and twenty-seven patients developed PFI from recurrent dislocations. Structural abnormalities were found in 38(95%) of patients. Patella alta (Caton-Deschamps index >1.2) was identified in 19(47%) patients, genu valgum in 12(30%) patients, increased tibial tubercle-trochlear groove distance(TT-TG>20mm) was present in 9(22.5%) patients and persistent femoral anteversion(> 20 deg) in 7(17%) patients. Eight patients were treated with TTO and MPFL reconstruction, three patients with MPFL reconstruction alone and five patients had guided growth for genu valgum correction. Ten patients are awaiting surgery. No postoperative patients had recurrence of PFI at their latest follow up. PFI is a common problem in the adolescent paediatric population with identifiable structural abnormalities. Correcting structural pathology with surgery leads to predictable and safe outcomes

Background. Recurrent patellar dislocation in combination with cartilage injures are difficult injuries to treat with confounding pathways of treatment. The aim of this study is to compare the clinical and functional outcomes of patients operated for patellofemoral instability with and without cartilage defects. Methods. 82 patients (mean age-28.8 years) with recurrent patellar dislocations, who underwent soft-tissue or bony procedures, were divided into 2 matched groups (age, sex, follow-up and type of procedure) of 41 each based on the presence or absence of cartilage defects in patella. Chondroplasty, microfracture, osteochondral fixation or Autologous Matrix-Induced Chondrogenesis(AMIC)-type procedures were done depending on the nature of cartilage injury. Lysholm, Kujala, Tegner and Subjective Knee scores of both groups were compared and analysed. Complications and return to theatre were noted. Results. With a mean follow-up of 8 years (2 years-12.3 years), there was a significant improvement observed in all the mean post-operative Patient Reported Outcome Measures (p<0.05) of both the groups, as compared to the pre-operative scores. Comparing the 2 groups, post-operative Lysholm, Kujala and Subjective knee scores were significantly higher in patients operated without cartilage defects (p<0.05). 3 patients operated for patellofemoral instability with cartilage defects had to undergo patellofemoral replacement in the long term. Odds ratio for developing complications is 2.6 for patients operated with cartilage defects. Conclusion. Although there is a significant improvement in the long term outcome scores of patients operated for recurrent patellar dislocation with cartilage defects, the results are significantly inferior as compared to those without cartilage defects, along with a higher risk of developing complications and returning to theatre

Aims. Classifying trochlear dysplasia (TD) is useful to determine the treatment options for patients suffering from patellofemoral instability (PFI). There is no consensus on which classification system is more reliable and reproducible for the purpose of guiding clinicians’ management of PFI. There are also concerns about the validity of the Dejour Classification (DJC), which is the most widely used classification for TD, having only a fair reliability score. The Oswestry-Bristol Classification (OBC) is a recently proposed system of classification of TD, and the authors report a fair-to-good interobserver agreement and good-to-excellent intraobserver agreement in the assessment of TD. The aim of this study was to compare the reliability and reproducibility of these two classifications. Methods. In all, six assessors (four consultants and two registrars) independently evaluated 100 axial MRIs of the patellofemoral joint (PFJ) for TD and classified them according to OBC and DJC. These assessments were again repeated by all raters after four weeks. The inter- and intraobserver reliability scores were calculated using Cohen’s kappa and Cronbach’s α. Results. Both classifications showed good to excellent interobserver reliability with high α scores. The OBC classification showed a substantial intraobserver agreement (mean kappa 0.628; p < 0.005) whereas the DJC showed a moderate agreement (mean kappa 0.572; p < 0.005). There was no significant difference in the kappa values when comparing the assessments by consultants with those by registrars, in either classification system. Conclusion. This large study from a non-founding institute shows both classification systems to be reliable for classifying TD based on axial MRIs of the PFJ, with the simple-to-use OBC having a higher intraobserver reliability score than that of the DJC. Cite this article: Bone Jt Open 2023;4(7):532–538

Imaging techniques including MR scanning and ultrasound were discussed. However it was noted that for standard orthopaedic practice in the UK plain films were the initial imaging available. The importance of taking a skyline view was stressed. The Dejour protocol was then outlined where the lateral Xray of the knee assesses the patellar height, the presence of dysplasia of the trochlear groove, and, if present, its boss height. A CT scan defines the patellar tilt angle, and with cuts through the tibial tubercle, the offset of the tibial tubercle from the trochlear groove (TTTG). The four abnormalities that can be defined are then corrected at operation. All patients undergo a lateral release. If the patellar tilt angle is greater than 20° then a medial reefing is performed. If the patellar height is greater than 1.2, a distalisation of the tibial tubercle to correct this to 1.0 is done. A MG of greater than 2Omm leads to a correction by an Elmsie medial tubercle transfer. A boss height of greater than 6mm suggests a trochleoplasty should be performed. However the Dejour protocol is yet to be validated. It was concluded that imaging is essential for analysing patellofemoral instability. Plain films alone do not give enough information. Patterns of patellofemoral instability as assessed by CT scan (and MRI scan) are yet to be established. Postoperative imaging to confirm correction of abnormalities should be done. The measurements are worthwhile but their validation is awaited

Trochlear dysplasia is a developmental condition characterised by an abnormally flat or dome shaped trochlea and is an important contributing factor to patellofemoral instability and recurrent patellar dislocation. We prospectively studied a cohort of 54 consecutive patients (59 knees) with patellofemoral instability secondary to trochlear dysplasia, treated with a trochleoplasty by a single surgeon over a 5 year period. Patients were recruited from the senior author's specialist knee clinic and pre-operatively, multiple patient-centred scores were recorded. After the trochleoplasty, these were repeated along with a patient satisfaction questionnaire. Of the 54 patients and 59 knees operated, 39 of the patients (44 knees) were female and 15 (15 knees) male and 40 patients (42 knees) had follow-up of 12 months or more. Their mean age at surgery was 21 years and 6 months and mean length of follow up 2 years. One patient was unable to attend for follow up due to the development of a pelvic Ewings sarcoma. A statistically significant improvement in outcomes was demonstrated when the pre and post-operative scores were compared (mean scores of Oxford 26 to 19, WOMAC 23 to 17, IKDC 54 to 72, Kujala 62 to 76, Lysholm 57 to 78, p values <0.001 for all scores). 93% (50 patients) were satisfied with the outcome of their procedure. We conclude that in the short and medium term, the results of trochleoplasty are encouraging in this challenging group of patients

Abstract. Background. Recurrent patellar dislocation in combination with cartilage injures are difficult injuries to treat with confounding pathways of treatment. The aim of this study is to compare the clinical and functional outcomes of patients operated for patellofemoral instability with and without cartilage defects. Methods. 82 patients (mean age-28.8 years) with recurrent patellar dislocations, who underwent soft-tissue or bony procedures, were divided into 2 matched groups (age, sex, follow-up and type of procedure) of 41 each based on the presence or absence of cartilage defects in patella. Chondroplasty, microfracture, osteochondral fixation or AMIC-type procedures were done depending on the nature of cartilage injury. Lysholm, Kujala, Tegner and Subjective Knee scores of both groups were compared and analysed. Complications and return to theatre were noted. Results. With a mean follow-up of 8 years (2 years-12.3 years), there was a significant improvement observed in all the mean post-operative Patient Reported Outcome Measures (p<0.05) of both the groups, as compared to the pre-operative scores. Comparing the 2 groups, post-operative Lysholm, Kujala and Subjective knee scores were significantly higher in patients operated without cartilage defects (p<0.05). 3 patients operated for PFJ instability with cartilage defects had to undergo patellofemoral replacement in the long term. Odds ratio for developing complications is 2.6 for patients operated with cartilage defects. Conclusion. Although there is a significant improvement in the long term outcome scores of patients operated for recurrent patellar dislocation with cartilage defects, the results are significantly inferior as compared to those without cartilage defects, along with a higher risk of developing complications and returning to theatre. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Treatment of patellar instability in adolescents is controversial. Some investigators have advocated early repair of the medial structures, whereas others have treated this injury nonoperatively. The medial patellofemoral ligament, is a primary restrictor and stabilizer of the patella, and has acquired a significant role in the treatment of instability in children and adolescents. The authors present a prospective study of 39 consecutive patients (45 knees), without physeal closure, who underwent plasty of the medial patellofemoral ligament for the treatment of symptomatic patellofemoral instability with autologous Gracilis tendon, according to Chassaing’s technique. There were 26 female and 13 male patients with an average age of 15, 9 years. Mean follow-up was 44 months (6–65). All patients presented with clinical evident patellar tilt. This population presented a TA-GT within a normal range (12+/− 5 mm), but presented in 80% of cases a trochlear dysplasia. Clinical functional results were evaluated using the Kujala scale. Arthroscopic evaluation was systematically performed searching for intra articular injuries or patellar tilt. Early rehabilitation protocols were used in all cases. At the last follow up evaluation, 90% of the patients presented good or very good results. Kujala Score was 84, 5 +/−9,7 after surgery compared with 54,9+/−11,8 before surgery (p< 0,0001). There were 3 minor complications: 2 hematomas and 1 superficial infection that resolved without complications. Four patients kept complaining of residual anterior knee pain as result of patellar chondropathy that was diagnosed intra operatively. Three patients complained of graft donor site pain. One patient presented with a patellar dislocation three years after the surgery, and two patients still present clinical instability two years after the procedure. There was no stiffness in the knee in any patient. The technique presented in this study has allowed very good clinical results, with few complications, using a small incision to reconstruct in an isometric fashion, this important patellar stabilizer

Objective. Overviewing the literature, pain and redislocation after surgical treatment of patellofemoral instability (PFI) is described with up to 30 %, especially with techniques involving the extensor mechanism, the lateral retinaculum or the medial vastus. However, outcome data about revision surgery is missing. Therefore, it was the purpose of this prospective study to evaluate the clinical outcome after revision surgery with an isolated or a combined reco. of the medial patellofemoral ligament (MPFL) with a follow up of 12 months. The indication for additional procedures such as distal femoral osteotomies (DFO), trochleoplasty, reclosing of the lateral retinaculum (RLR) or lateralisation of the tuberosity (LT) were performed depending on the clinical and radiological pathomorphologies. Methods. In between 3/07–4/09, 42 pat. with a mean age of 24 years (13–46ys) were revised due to persistent PFI after mean 1.8 failed previous operations (lateral release, medial gather/VMO-distal., medial. of the tuberosity) in our department. An isolated reco. of the MPFL was performed in 15 cases, while a combination with a DFO due to massive femoral axis deformity (n=5), trochleoplasty due to a convex trochlear morphology (n=1) and/or LT (n=4) and/or RLR due to medial instability or lateral pain (n=22) was done in 27 cases. The clinical result was evaluated by the pre- and postop. IKDC/Kujala/Tegner-score and by a subjective questionnaire. Radiologically, the patellashift/-tilt/-height and level of the eventual degeneration were defined preop. and at the point of follow up with the help of straight lateral radiographs and by MRI. Significance level was set at p=.05, statistical calculation was done by the use of the t-test. Results. 87 % were very satisfied/satisfied with the treatment., None redislocation of the patella occurred during the follow up. We could evaluate a significant decrease of the pain during daily activities. The IKDC/Kujala/Tegner score have shown a significant increase overall. However, a significant difference concerning the scores could not be noticed in between the groups without and with additional procedures. Patellar shift, tilt, height decreased significantly to anatomical values. The level of preexisting degeneration showed no aggravation. Conclusion. Since it is known that PFI is a multifactorial problem, revision surgery should set about only after comprehensive examinations. Regarding our results, isolated or combined MPFL reco. seems to be a very effective treatment of recurrent patella dislocation and results in a significant increase of stability, functionality as well as in a reduction of pain. Additional pathomorphologies of the bony structures or a lateral release, which causes pain or an aggravation of instability, have to be addressed additionally to reach same results like with an isolated therapy. Level of Evidence. II

Background: No studies exist about the long-term correlation of patellofemoral osteoarthrosis to poor outcome after traditional realignment surgery for chronic patellofemoral instability. The objective of this study was to evaluate the recurrent instability and symptomatic osteoarthrosis over a long follow-up period. Methods: Fifty-two patients underwent distal realignment surgery for chronic patellar instability, 28 with Roux-Goldthwait procedure and 24 with Krogius procedure. A follow-up evaluation was performed at a mean 12 years (range, 8 to 22 years) after surgery, in which 39 of 52 patients participated. Recurrent instability and osteoarthrotic characteristics were evaluated by plain radiographs and magnetic resonance images obtained at follow-up. The original hospital data were reviewed to assess patients’ background. Subjective symptoms were assessed with patellofemoral scores. Results: Of the 39 controlled patients, 10 had chronic patellar instability, including 4 patients who underwent reoperation during follow-up. The mean patient age at follow-up was 33 years (range, 26 to 43). Patellofemoral full-thickness cartilage lesions were found on MRI in 29 (75%) of patients and all of the patients had mild lesions. A joint space narrowing was present in 6 cases in plain radiographs indicating severe patellofemoral osteoarthrosis. Only 48% of the patients reported satisfaction with the patellar stability and anterior knee symptoms and the unsatisfactory result was associated with patellofemoral osteoarthrosis (P=0.05). The mean Kujala score was 83 (range 52–100) points. The surgical technique employed did not affect the overall outcome. Conclusion: The long-term outcome of traditional realignment surgery for chronic patellofemoral instability seemed to be strongly associated with patellofemoral osteoarthrosis. Despite the relatively rare occurrence of recurrent instability, less than half of patients achieved a satisfactory result. Patellofemoral osteoarthrosis seems to be the long-term consequence in patients treated with traditional surgical procedures for patellar instability. In future studies focusing on patellar stability, preventive methods against the development of patellofemoral osteoarthrosis should be emphasized

Aims: The purpose of the study was to assess the mid-term knee functional results after Medial Patellofemoral Ligament (MPFL) reconstruction with single semitendinosus autograft in patients with patellofemoral instability. Methods and Results: Knee function was assessed in 45 patients (46 knees) who underwent MPFL reconstruction with semitendinosus autograft. The tibial insertion of the semitendinosus was preserved whereas the free end, after stripping of the tendon from the musculo-tendinus junction was rerouted through the most distal part of the medial intermuscular septum proximally to the adductor tubercle, to the superomedial border of the patella, where it was fixed. Clinical and radiological evidence of patellar instability and MPFL rupture or deficiency was documented prior to surgery. Knee function was assessed preoperatively and postoperatively with the use of Kujala, Tegner, Lysholm and International Knee Documentation Committee (IKDC) scores. There were 34 male and 11 female patients with an average age of 32.5 years, ranging from 17 to 60 years. The minimum follow up was 2 years with an average of 33.5 months (range 24–54 months). Fourteen patients (30%) presented a degree of patellofemoral dysplasia. All knee functional scores significantly improved postoperatively. Kujala score improved from 57.7 to 77.1, Tegner score improved from 3.06 to 5.26, IKDC score improved from 51.2 to 75.44 and Lysholm score improved from 58.7 to 79.3. One of the patients required revision of the MPFL reconstruction due to traumatic redislocation of the patella. Conclusions: At a midterm follow-up, reconstruction of the MPFL with rerouting of the semitendinosus tendon is an effective method with improved function in all patients. Maximum improvement was achieved within the first six postoperative months. Heterogeneity of our population may have affected some of our results

Introduction: Patellofemoral instability (PFI) is a disabling condition that occurs in adolescence. Recurrence after patellar dislocation has been reported in 2–50% of cases. This study aimed to compare the shape of the distal femur in PFI to a normal cohort. Method: 108 CT scans from 54 subjects with PFI were compared to 197 CT scans from 102 normal subjects. Outlines of the trochlear groove and lateral condyle were extracted from CT scans using Interactive Data Language version 5.0 image manipulation software. The shapes were aligned using a modified Procrustes analysis and interpolation performed with a basic cubic spline. A statistical method from the field of functional data analysis was used to quantify shape. A discriminant analysis was then used to provide a tool for deciding which patients had abnormal grooves thus improving patient selection for trochleoplasty. Results: Mathematical quantification showed a significant difference at the 0.001 level using an independent t-test between the normal and PFI groups for the shape of the trochlear groove with PFI knees having a more complex shape than normal. The second largest source of variation is in the position of the trochlear groove minimum with respect to the coronal plane together with variation in the shape of the medial condyle. The trochlear groove is situated more medially, with a shallower medial condyle, in PFI. In contrast the trochlear groove is situated more laterally, with a more prominent medial condyle in normal knees. Analysis of shape of the lateral condyle showed that in PFI, it is shorter and broader. Conclusion: Principal components analysis can be used to quantify the variation in shape of the distal femur and allow a discriminant function analysis to be performed comparing PFI knees to normal knees. This quantification of shape can be applied to diagnosis of instability, operative planning for trochleoplasty and implant design

Objectives. For a long time lateral release (LR) was performed as a standard procedure both, for patellofemoral pain syndrome (PFPS) and patellofemoral instability (PFI). However, recent biomechanical studies have shown that LR is not useful for decreasing the lateral force onto the patella, but is increasing not only medial but also lateral PFI. Furthermore, pain on palpation over the lateral patellofemoral joint space can result in patients treated with extensive LR. We postulate that in case of persistent PFI or PFPS after failed LR the reconstruction of the lateral retinaculum as an addition of the reconstruction of the medial patellofemoral ligament (MPFL) is necessary in terms of decreasing medial PFI as well as lateral pain. Materials and Methods. In between 03/07 and 04/09 we have seen a total of 25 patients (20 f, 5 m) with persistent PFI and palpatory pain over the lateral retinaculum due to unsuccessful treatment of PFI with a LR. These patients have undergone revision surgery with an anatomical reconstruction of the released lateral retinaculum in combination with a reconstruction of the medial patellofemoral ligament (MPFL) in an aperture-technique using the gracilis tendon. The average age at time of operation was 26.2 ± 9.8 years. Preoperatively, as well as 6 weeks, 3 months, 6 months, and 12 months postoperatively, clinical examinations were performed and subjective as well as objective scores (Kujala-, Tegner-, IKDC-score) were evaluated. Regarding radiological parameters measurement of patellar tilt and shift was carried out on axial radiographs before and after the operation. Results. During the first twelve months after the operation only one redislocation could be recorded. Pain on palpation over the reconstructed lateral retinaculum was remaining in four patients (16%). Although several patients complained about persistent patellofemoral pain on exertion or after enduring flexion of the knee, all of them reported about an improvement of their pain situation. This fact is reflected in a highly significant improved but still moderate IKDC- (from 46.5 ± 14.9 to 68.9 ± 22.7, p<0.001) and Kujala-score (from 47.7 ± 15.3 to 74.8 ± 24.8, p<0.001) at the one year follow up. As far as sports activity is concerned, a statistically significant improvement of the Tegner-score up to 4.7 ± 2.4 (preoperative 2.3 ± 1.5, p<0.001) could be achieved. The radiological analysis showed a highly significant decrease of both, patellar tilt (from 15.4 ± 6.5 to 10.3 ± 6.2, p<0.001) and patellar shift (from 4.3 ± 3.3 to 2.5 ± 1.3, p=0.002). Conclusions. After one or more unsuccessful previous efforts of stabilizing the patella by LR, the technique performed in this essay leads to a considerable improvement of subjective scores and objective clinical and radiological parameters as well as sports activity

Abstract

Chronic patello-femoral joint instability leads to recurrent subluxation and dislocation affecting knee function and preventing participation at sport. Traumatic dislocation of the patella results in rupture of the medial patello-femoral ligament (MPFL) in the majority of cases with a high incidence of chronic instability after a second dislocation. MPFL reconstruction can prevent recurrent dislocation and improve knee function. We report on our experience in MPFL reconstruction using hamstring tendons and its effect on the knee function in patients with chronic patello-femoral joint instability.

In this prospective study from 2005 to 2008, 68 patients (69 knees) with chronic patello-femoral instability were treated with MPFL reconstruction through a minimally invasive and arthroscopically assisted approach. In this procedure the semintendonosis with or without the gracilis tendon is routed from the pes anserinus to the most distal portion of the medial intramuscular septum before being secured to the superomedial border of the patella. All patients were evaluated pre-operatively and then post-operatively for a mean of 25 months (range 12-48 months). Knee function was assessed by the Tegner, Kujala and Lysholm scores.

There were 44 (65%) women and 24 (35%) men. Average age was 27 years. There were 2.7 mean pre-operative patellar dislocations (range 2-7). Mean follow-up was 19.6 months (range 12 to 56 months). IKDC score improved from 48.2 to 74.2, Kujala scores improved from 55.4 to 85.3. Lysholm scores improved from 52.4 to 77.3. Tegner activity scores improved from 2.5 to 5.4. There were overall 87% good to excellent results. No recurrent dislocations or wound related complications.

Medial patello-femoral reconstruction can provides excellent results in the treatment of patello-femoral joint instability with poor knee function.

Acute dislocation of the patella is a common injury in adolescents and adults and occurs most commonly during sports participation. The injury is most commonly an indirect injury occurring with a pivoting away from the involved knee. Risk factors include young age, generalized laxity, patella alta, patellar subluxation, and trochlea or patellae dysplasia.

The essential lesion of the lateral patellar dislocation is a tear of the medial patellofemoral ligament coursing from the medial patella to the medial epicondyle. The medial patellofemoral ligament is superficial to synovium and the femoral attachment lies posterior to the medial synovial reflexion and is not seen at arthroscopy. The retinaculum becomes confluent with the medial patellofemoral ligament distally. There are frequently bone fragments detached from the medial patella and lateral femoral condyle at the lateral margin and just anterior to the terminal sulcus. Patellar subluxation with an increased TT-TG distance is common.

Studies applied to an entire group of dislocations have not shown acute surgery to be of great benefit. Conservative treatment is usually recommended. I made an exception in the case of large patellar chondral injuries with significant subluxation. Removal of loose bodies, lateral retinacular release and medial patellofemoral ligament repair or reconstructon with a hamstring graft are then recommended.

In cases of recurrent dislocation I recommend an Elmslie-Trillat procedure in addition when there is significant subluxation and closed physes.

Clinical management of patellofemoral (PF) instability is a challenge, particularly considering the wide range of contributing variables that must be taken into consideration when determining optimal treatment. An important outcome measure to consider in this patient population is disease-specific quality of life (QOL). The purpose of this study was to factor analyse and reduce the total number of items in the Banff Patellar Instability Instrument (BPII). Subsequent to the factor analysis, the new, item-reduced BPII 2.0 was tested for validity, reliability and responsiveness.

Disease-specific QOL was measured in patients with a confirmed diagnosis of PF instability (n = 223) at the initial consultation with the original BPII. Data from these BPII scores was used to employ a principal component analysis (PCA) to factor analyse and reduce the total number of items in the original BPII, to create the new BPII 2.0. The BPII 2.0 underwent content validation (Cronbach's Alpha, patient interviews and reading-level); construct validation (ANOVA comparing the initial consultation, 6, 12 and 24 month post-operative, Eta squared); convergent validation (Pearson r correlation to the original BPII); responsiveness testing (Eta squared, anchor-based distribution testing); and reliability testing (intra-class correlation coefficient (ICC) 2,k).

The original BPII was successfully reduced from 32 to 23 items. The new BPII 2.0 demonstrated excellent Cronbach's Alpha values: initial consult = 0.91; 6-months = 0.96; 12-months = 0.97; and 24-months post-operative = 0.76. Grade-level reading assessment for all items in the BPII 2.0 was below grade twelve. The ANOVA determined the BPII 2.0 was able to discriminate between the initial consultation, 6, 12 and 24 months post-operative assessments, with significant differences between each time-point (p < 0.05). Eta squared was 0.40, demonstrating a medium to large effect size. Convergent validity was established with the BPII 2.0 significantly correlated to the original BPII (initial consult = 0.82, 6-month = 0.90, 12-month = 0.90, and 24-month = 0.94). Anchor-based responsiveness was established with a significant correlation between the 7-point scale of patient-perceived improvement and 24-month post-operative BPII 2.0 scores. Strong reliability was established with an ICC (2,k) = .97.

The BPII has undergone a critical step in its psychometric and clinimetric evolution: structural validation. With the work completed in this study, the BPII and BPII 2.0 have completed assessment of seven of the nine Consensus-based Standards for the selection of health Measurement INstruments (COSMIN) properties including: 1) Internal consistency; 2) Reliability; 3) Standard error of measurement; 4) Content validation; 5) Structural validity; 6) Criterion validity; and, 7) Responsiveness testing. Completion of these assessments and the introduction of a structurally valid and shorter questionnaire, the BPII 2.0, provides a definitive level of credibility to this disease-specific outcome measure.

Introduction

The dysplastic trochlear is a developmental condition characterized by an abnormally flat or dome-shaped trochlea and it is recognized as a significant cause of patella instability. Surgical correction of the shape of the Trochlear Groove is frequently performed. The described methods in the literature involve open arthrotomy to normalize and maintain the trochlear morphology achieving normal alignment and tracking of the patella.