Recurrent patellar instability is a common problem and there are multiple demographic and pathoanatomic risk factors that predispose patients to dislocating their patella. The most common of these is trochlear dysplasia. In cases of severe trochlear dysplasia associated with patellar instability, a sulcus deepening trochleoplasty combined with a medial patellofemoral ligament reconstruction (MPFLR) may be indicated. Unaddressed trochlear pathology has been associated with failure and poor post-operative outcomes after stabilization. The purpose of this study is to report the clinical outcome of patients having undergone a trochleoplasty and MPFLR for recurrent lateral patellofemoral instability in the setting of high-grade trochlear dysplasia at a mean of 2 years follow-up. A prospectively collected database was used to identify 46 patients (14 bilateral) who underwent a combined primary MPFLR and trochleoplasty for recurrent patellar instability with high-grade trochlear dysplasia between August 2013 and July 2021. A single surgeon performed a thin flap trochleoplasty using a lateral para-patellar approach with lateral retinaculum lengthening in all 60 cases. A tibial tubercle osteotomy (TTO) was performed concomitantly in seven knees (11.7%) and the MPFLR was performed with a gracilis tendon autograft in 22%, an allograft tendon in 27% and a quadriceps tendon autograft in 57% of cases. Patients were assessed post-operatively at three weeks and three, six, 12 and 24 months. The primary outcome was the Banff Patellar Instability Instrument 2.0 (BPII 2.0) and secondary outcomes were incidence of recurrent instability, complications and reoperations. The mean age was 22.2 years (range, 13 to 45), 76.7% of patients were female, the mean BMI was 25.03 and the prevalence of a positive Beighton score (>4/9) was 40%. The mean follow-up was 24.3 (range, 6 to 67.7) months and only one patient was lost to follow-up before one year post-operatively. The BPII 2.0 improved significantly from a mean of 27.3 pre-operatively to 61.1 at six months (p < 0 .01) and further slight improvement to a mean of 62.1 at 12 months and 65.6 at 24 months post-operatively. Only one patient (1.6%) experienced a single event of subluxation without frank dislocation at nine months. There were three reoperations (5%): one for removal of the TTO screws and prominent chondral nail, one for second-look arthroscopy for persistent J-sign and one for mechanical symptoms associated with overgrowth of a lateral condyle cartilage repair with a bioscaffold. There were no other complications. In this patient cohort, combined MPFLR and trochleoplasty for recurrent patellar instability with severe trochlear dysplasia led to significant improvement of patient reported outcome scores and no recurrence of patellar dislocation at a mean of 2 years. Furthermore, in this series the procedure demonstrated a low rate (5%) of complications and reoperations

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 this purpose to guide clinicians in order to treat PFI. There are also concerns about 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 intra-observer agreement in the assessment of TD. The aim of this study was to compare the reliability and reproducibility of these two classifications. 6 assessors (4 consultants and 2 registrars) independently evaluated 100 magnetic resonance axial images of the patella-femoral joint for TD and classified them according to OBC and DJC. These assessments were again repeated by all raters after 4 weeks. The inter and intra-observer reliability scores were calculated using Cohen's kappa and Cronbach's alpha. Both classifications showed good to excellent interobserver reliability with high alpha scores. The OBC classification showed a substantial intra-observer 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 to those by registrars, in either classification systems. This large study from a non-founding institute shows both classification systems to be reliable for classifying TD based on magnetic resonance axial images of the patella-femoral joint, with the simple to use OBC having a higher intra-observer reliability score compared to the DJC

Patellofemoral instability is common injury and proximal soft tissue stabilisation via MPFL reconstruction or imbrication is the mainstay of treatment. The contribution of certain pathoanatomies to the failure of patellofemoral stabilisation is unknown. The purpose of this study was to analyse the failure rate of patellar stabilisation procedures in a large cohort as measured by re-dislocation of the patella. A secondary purpose was to identify the pathoantomical features that may have predisposed these patients to failure. Between May 2008 and March 2014, 207 MPFL reconstructions and 70 MPFL imbrications were performed by a single surgeon. Post-operative assessment included clinical examination to assess the integrity of the MPFL graft, plain radiographs and the Banff Patellofemoral Instability Instrument (BPII), a disease-specific outcome measure. Failures were identified and risk factors including trochlear dysplasia, patella alta, generalised ligamentous laxity (GLL), femoral tunnel position and rotational abnormalities were evaluated as contributing factors. There were 48 male and 178 female patients. The mean duration of follow-up was 24.1 months (SD 9.4, range 12–74). The average age at time of surgery was 24.81 years (SD 8.87, range 50.35–8.99). The average BMI was 23.75 (SD 3.62, range 36.70–14.90). There were 10 failures in the MPFL reconstruction group (4.8%), 1 male and 9 females. Femoral tunnel position was assessed in relation to Schottle's point as good or excellent in all 10 cases. In terms of pathoanotomy, 8/10 failures had high-grade trochlear dysplasia, 1/10 had patella alta, 6/10 had a Beighton score of >/= 4, and 3/10 had clinically significant rotational abnormalities of the lower extremity. The primary cause attributed to the 10 failure cases was trauma in two, trochlear dysplasia in three, rotational abnormalities in one, combined femoral anteversion and GLL in two, and combined trochlear dysplasia and GLL in two. There were 13 failures in the MPFL imbrication group (18.6%), 2 males and 11 females. Among these failures, 4/13 had high-grade trochlear dysplasia, 3/13 had patella alta, 10/13 had a Beighton score of >/= 4, and one had clinically significant rotational abnormalities of the lower extremity. The primary pathology that was considered to contribute to the imbrication failure cases was trochlear dysplasia in four, generalised ligamentous laxity in six, rotational abnormalities in one, patella alta with trochlear dysplasia in one, and generalised ligamentous laxity with trochlear dysplasia in one. Prior to surgical failure the mean BPII score for the failure group was 71.5/100, compared with 74.6/100 for the remainder of the cohort. MPFL reconstruction is highly successful surgical procedure for stabilising the unstable patella with a failure rate of only 4.8%. Higher failure rates are seen in patients undergoing imbrication of the MPFL compared to a reconstruction. Pathoanatomies that contribute to failure vary between patients with the most common being trochlear dysplasia and generalised ligamentous laxity

Abstract. Background. The primary objective of the study is to determine the function outcome and survivorship of patellofemoral replacement. The secondary aim is to find the determinants of successful/poor outcome. Methods. This retrospective study involved 45 patients who underwent AVON patellofemoral replacement between January 2015 to December 2020 with the minimal follow-up off for 12 months. The functional outcome was measured using Oxford Knee score (OKS), EuroQol five dimension (EQ-5D). IWANO and Kellgren-Lawrence classification was used to analyse radiographs. To identify determinants of outcome, the following subgroups the presence or absence of normal alignment, tibiofemoral arthritis, trochlear dysplasia and previous surgery. Complications and revision rates were also recorded. Results. The mean follow-up period was 41.7 +/− 8.3 months with no patients lost in follow-up. Patellofemoral replacement significantly improved the Oxford Knee score (OKS), EuroQol five dimension (EQ-5D) (p<0.001). Four out of 45(8.9%) patients underwent revision surgery. Patients with normal alignment preoperatively did worse than those with abnormal alignment with patellar instability. Patients with grade two tibiofemoral arthritis, history of previous surgery did significantly worse with poorer functional outcome. Conclusion. Patellofemoral arthroplasty is reliable treatment option which improves patient function and quality of life with good survivorship in isolated patellofemoral arthritis in mid-term follow-up

Background. The goal of patellofemoral arthroplasty (PFA) is to replace damaged cartilage, and to correct underlying deformities, to reduce pain and prevent maltracking. We aimed to determine how PFA modifies patellar height, tilt, and tibial tuberosity to trochlear groove (TT-TG) distance. The hypothesis was that PFA would correct trochlear dysplasia or extensor mechanism malalignment. Methods. The authors prospectively studied a series of 16 patients (13 women and 3 men) aged 64.9 ± 16.3 years (range, 41 to 86) that received PFA. All knees were assessed pre-operatively and six months post-operatively using frontal, lateral, and ‘skyline’ x-rays, and CT scans to calculate patellar tilt, patellar height and tibial tuberosity–trochlear groove (TT-TG) distance. Results. The inter-observer agreement was excellent for all parameters. (ICC > 0.95). Pre-operatively, the median patellar tilt without quadriceps contraction (QC) was 17.5° (range, 5.3°–33.4°) and with QC was 19.8° (range, 0°–52.0°). The median Caton- Deschamps Index (CDI) was 0.91 (range, 0.80–1.22) and TT-TG distance was 14.5mm (range, 4.0–22.0). Post-operatively, the median patellar tilt without QC was 0.3° (range, −15.3°–9.5°) and with QC was 6.1° (range, −11.5°–13.3°). The median CDI was 1.11 (range, 0.81–1.20) and TT-TG distance was 10.1mm (range, 1.8–13.8mm). Conclusion. The present study demonstrates that, beyond replacing arthritic cartilage, trochlear-cutting PFA improves patellofemoral congruence by correcting trochlear dysplasia and standardizing radiological measurements as patellar tilt and TT-TG. The association of lateral patellar facetectomy diminishes local effects of OA and improves patellar tracking by reducing the patellar tilt

Purpose. The purpose of this study is to investigate whether traditional morphometric parameters of the femur trochlear surface are dependable to classify the severity of the trochlear dysplasia. Methods. An automatic method to process the distal femur surface is proposed to determine anatomical landmarks and compute morphometric parameters, namely the trochlear depth(TD), the trochlear sulcus angle(SA), the lateral trochlear facet inclination(LFTI), the trochlear facet asymmetry ratio(TFAR) and the ratio between the two (lateral and medial) maximum antero-posterior sizes(CAR) routinately used to quantify trochlear dysplasia. Tests on 11 cadavers and 43 patients, affected by aspecific anterior knee pain, elucidate the role of the parameter cut-off values traditionally used in clinical practice. Results. Clinical cut-off values lead to incoherent classifications in between the parameters along with some inconsistency with expert-based classifications. The classification based on TD cut-off is in agreement with the clinical evaluation whereas the SA classification provided a falsepositive rate of about 55%. Patients dataset analysis shows that the classifications based on TD and SA cut-off were prone to high rate of false positive (55%) and false negative (39%), respectively. LFTI, TFAR and CAR did not comply with TD and SA parameters. A positive correlation between TD decrease and dysplastic condition severity was however found whereas SA was found little correlated. Conclusion. The classification of trochlear dysplastic condition drawn by morphometric parameters exhibited notable uncertainty. More sophisticated morphologic analysis of the trochlear region for instance on three-dimensional surface modeling techniques might increase the reliability of the classification

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

This talk reviews the topic of patellofemoral arthroplasty from a historical, technical, and clinical perspective. Emphasis is placed on the design rationale, surgical technique, and 11 year clinical results of so-called “patient-matched” or “patient-specific” patellofemoral arthroplasty in which the trochlear implant is matched to the anatomy of the individual patient through the use of pre-operative computerized imaging scans. The implants are inlayed into the articular cartilage without any intra-operative femoral bone resection. Clinical results involving patient-matched patellofemoral arthroplasty are presented with an average follow-up of 11 years. Case studies reviewing our experience with patient-matched trochlear implants in the setting of femoral trochlear dysplasia are also presented. Patient-specific patellofemoral arthroplasty is a safe and effective treatment for patients with isolated patellofemoral arthritis. The results compare favorably with off-the-shelf patellofemoral arthroplasties that have been reported on over the past thirty years and can be carried out more efficiently. We believe the key elements that contribute to the success of patient-matched patellofemoral arthroplasty are as follows: (a) a strict inclusion criteria based on pre-operative radiographic evaluation; (b) a meticulous attention to soft-tissue balance and patellofemoral tracking at the time of arthroplasty; and (c) a patient-specific design and manufacturing methodology that ensures accurate and precise anatomic fit while simultaneously providing proper patellofemoral alignment and medial-lateral constraint

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. Material, methods and results. Open procedures carries a significant risk of arthrofibrosis. We describe an arthroscopic procedure to create a neo-trochlea using gouges, spherical and conical hooded burrs. We studied prospectively a series of 4 consecutive patients with patello-femoral instability secondary to trochlear dysplasia, who were treated by an Arthroscopic trochleoplasty by a single surgeon between 2007 and 2008. Postoperatively the patients were rehabilitated in accordance with our routine Patello-Femoral microfracture protocol. CT scanning at one year showed a complete neo-cortex and cartilage sequenced MRI at 12 months showed complete fill with fibro cartilage. Pre- and post-operative scores (KOOS, Kujala) were assessed by the patients and a satisfaction questionnaire was completed. The results showed a statistical improvement in the outcome at the 3 year follow up. Conclusion. Overall, patients (100%) were satisfied with the outcome of their procedure and there have been no adverse events. To our knowledge this technique has not been described before in the English literature and the early results of arthroscopic trochleoplasty are encouraging and offer an alternative to open approaches. Larger numbers and longer follow ups are needed to confirm the long term benefit

Patella instability is a common problem with many surgical options. We prospectively evaluated the results of medial patella femoral ligament (MPFL) reconstruction with an autogenous gracilis or semitendinous graft. With a minimum follow up of one year patients were reviewed using the Kujala scoring system. Twenty MPFL reconstructions were performed on seventeen patients over a two year period, from January 2004 to December 2005. There were 13 females and 4 males. Three patients had bilateral involvement. Thirteen patients had a lateral release with their MPFL reconstruction and three had a distal realignment procedure as well to correct their patella instability. The mean follow up was 17 months (range 12 to 26 months). The average age was 25 years old at operation (range 13 to 47) and the average age of their first dislocation was 16 (range 0-35). Nine patients had previous surgical treatment for patella instability. The average hypermobility score in the patients was 5/9 and six patients scored 9/9. At follow up 18 out of 20 patients (90%) had stable tracking with no further subluxations/dislocations. Of the two with unstable tracking, one had a stable patella before falling several times onto her knee. An MRI confirmed the ligament was intact but a type 2 trochlear dysplasia was present and a Bereiter trochleoplasty was subsequently performed. The other patient described no frank dislocation but instead subluxations. Eighteen of the twenty reconstructions (90%) achieved a stable patella. Overall Kujala scores increased by a third

Total knee arthroplasty (TKA) has produced excellent results, but many surgeons are hesitant to perform TKA in younger patients with isolated patellofemoral arthritis. In properly selected patients, patellofemoral arthroplasty (PFA) is an effective procedure with good long-term results. Contemporary PFA prostheses have eliminated many of the patellar maltracking problems associated with older designs, and short-term results, as described here, are encouraging. Long-term outcome and prospective trials comparing TKA to PFA are needed. Incidence. Isolated patellofemoral arthritis occurs in as many as 11% of men and 24% of women older than age 55 years with symptomatic osteoarthritis (OA) of the knee; Isolated patellofemoral arthritis found in 9.2% of patients older than age 40 years; 7% to 19% of patients experience residual anterior knee pain when TKA is done for isolated patellofemoral arthritis. Imaging. Weight bearing AP radiographs as supine radiographs can underestimate the extent of tibiofemoral arthritis; Midflexion posteroanterior radiographs to rule out posterior condylar wear; Lateral radiographs to identify the presence or absence of patella alta or baja; Axial radiographs identify the presence of trochlear dysplasia, patellar tilt or subluxation, and extent of patellofemoral arthritis; Magnetic resonance imaging and arthroscopic photographs should be reviewed if available. Indications. Osteoarthritis limited to the patellofemoral joint; Symptoms affecting daily activity referable to patellofemoral joint degeneration unresponsive to lengthy nonoperative treatment; Posttraumatic osteoarthritis; Extensive Grade-III chondrosis; Failed extensor unloading surgical procedure; Patellofemoral malalignment/dysplasia-induced degeneration. Contraindications. No attempt at nonoperative care or to rule out other sources of pain; Arthritis of greater than Grade 1 involving tibiofemoral articulation; Systemic inflammatory arthropathy; Osteoarthritis/chondrosis of the patellofemoral joint of Grade 3 or less; Patella baja; Uncorrected patellofemoral instability or malalignment; Uncorrected tibiofemoral mechanical malalignment; Active infection; Evidence of chronic regional pain syndrome or evidence of psychogenic pain; Fixed loss of knee range of motion, minimum 10–110 degrees ROM. Results. Majority of failures related to patellar instability from uncorrected patellar malalignment, soft-tissue imbalance, or component malposition; With improved implant designs tibiofemoral arthritis has become the primary source of failure; Failure from component subsidence or loosening occurring in <1% of knees. Our Series. Retrospective review 34 patients, 40 knees average 30 month follow-up using Natural Knee II Patello-femoral Joint System (Zimmer, Warsaw, IN); Average age 61, ranging from 34–84 years of age; Average subset KOOS scores were 93 for pain, 94 for symptoms, 94 for ADL's, 70 for sports and recreation, 82 for quality of life; Average pre-operative Tegner score 2.6, increasing to 4.7 post-operatively; 38/40 survival over 30 months with the two failures undergoing revision for traumatic injuries; No revisions to TKA; At most recent follow-up no progression of OA to involve tibiofemoral compartments; No evidence of component loosening