Background:. During the past two decades the medial Patellofemoral ligament has come to the fore as the essential lesion of acute patella dislocation and its reconstruction in cases of chronic instability seems logical. The femoral insertion of the medial Patellofemoral ligament (MPFL) is key to the isometry or desired anisometry of the reconstruction. Radiographic landmarks for the femoral insertion has been described in literature most notably by Schottle et al. AJSM 2007. We examined the consistency of these landmarks of the femoral insertion of the MPFL. Methods:. 24 unpaired knees of cadavaric specimen were dissected for the origin of the MPFL. A radiographic marker was then placed in the centre of the femoral attachment of the MPFL and a direct lateral X-ray obtained of the distal femur. The sweet spot was defined according to the landmarks described by Schottle et al and deviation from the sweet spot was measured. Results:. The average distance from the centre of the described radiological centre of the MPFL was 5.4 mm. In six cases the ligament insertion was 5.6 mm distal to the ideal radiological centre. We did not find the origin of the MPFL to be a consistent radiological landmark due to a wide insertion of the ligament on the femur with a variable anisometric centre. We recommend dynamically testing the insertion site of the MPFL around a guide wire inserted into the femur instead of relying solely on the radiological position

Summary. Nearly one-third of patients in this series with an ACL rupture requiring reconstruction had evidence of MPFL injury. This should be considered when patients are seen, and when MRI scans are reviewed/reported. Introduction. The Medial Patello-Femoral Ligament (MPFL) is the largest component of the medial parapatellar ligamentous complex. The senior surgeon felt that there was an anecdotally high rate of MPFL injury amongst his patients undergoing Anterior Cruciate Ligament (ACL) repair, but no discussion of this in the present literature. Method. A literature search was performed; although there were both scanty radiographic and anatomical studies of the MPFL, we found no literature looking at ACL and MPFL concurrent injury rates. The Magnetic Resonance Imaging (MRI) scans of fifty consecutive ACL reconstruction patients were retrospectively reviewed. Two independent radiologists were asked to review the scans looking specifically for evidence of MPFL rupture or Injury. The degree of injury was rated as rupture or by degree of sprain as applicable. One patient was excluded due to motion artefact limiting certainty. Results. Of the remaining forty-nine patients, 35 (71%) were intact, but fourteen (29%) showed evidence of injury. Five (10%) had a low-grade sprain, six (12%) had high-grade sprain, and three (6%) had complete rupture. The radiologists also noted that there was some variation in scanning protocols, and those with fat suppressed scans had better diagnostic value; this offered an opportunity to change the scanning practice. Conclusion. Nearly one-third of patients in this series with an ACL rupture requiring reconstruction had evidence of MPFL injury. This should be considered when patients are seen, and when MRI scans are reviewed/reported. Further, we would suggest that fat suppression sequences are included as standard to improve imaging quality

Recent literature suggests MPFL is the primary medial restraint in lateral patellar dislocation and supports acute repair in first lateral dislocations. Objective: To evaluate the results of patients who underwent acute surgical repair of MPFL in our unit. Materials and Methods: Nine patients with mean age of 25(12–41) were evaluated in a dedicated clinic. The mean follow-up was 15.7 months (6–22). All patients had MRI scan preoperatively and were operated within two weeks of injury. Patients were evaluated clinically and Kujala and Lysholm scores were recorded. Results: None of these patients had further dislocations of patella and patellar apprehension test was negative on examination. The mean Kujala score was 78(74–100) and mean Lysholm score was 92(85–100). All patients had returned to sporting activities at clinic review. All but one mentioned that they would choose surgical repair if the injury occurred in the other knee. Conclusion: Our results confirm in selective patients acute repair of MPFL is the ideal treatment to prevent recurrent dislocations and early return to sports

Medial patellofemoral ligament (MPFL) reconstruction is used to treat patellar instability and recurrent patellar dislocation. Anatomical studies have found the MPFL to be a double-bundle structure. We carried out a meta-analysis of studies reporting outcomes of patellofemoral reconstruction using hamstring tendon autograft in a double-bundle configuration and patellar fixation via mediolateral patellar tunnels. A literature search was undertaken with no language restriction in various databases from their year of inception to July 2012. The primary outcome examined was the post-operative Kujala score. We identified 320 MPFL reconstructions in nine relevant articles. The combined mean post-operative Kujala score was 92.02 (standard error (. se. ) 1.4, p = 0.001) using a fixed effects model and 89.45 (. se. 37.9, p = 0.02) using random effect modelling. The reported rate of complications with MPFL reconstruction was 12.5% (40 of 320) with stiffness of the knee being the most common. High-quality evidence in assessing double-bundle MPFL reconstruction is lacking. The current literature consists of a mixture of prospective and retrospective case series. High-quality randomised trials evaluating this procedure are still awaited. Cite this article: Bone Joint J 2013;95-B:900–5

Hypermobility is an acknowledged risk factor for patellar instability. In this case control study the influence of hypermobility on clinical outcome following medial patellofemoral ligament (MPFL) reconstruction for patellar instability was studied. A total of 25 patients with hypermobility as determined by the Beighton criteria were assessed and compared with a control group of 50 patients who were matched for age, gender, indication for surgery and degree of trochlear dysplasia. The patients with hypermobility had a Beighton Score of ≥ 6; the control patients had a score of < 4. All patients underwent MPFL reconstruction performed using semitendinosus autograft and a standardised arthroscopically controlled technique. The mean age of the patients was 25 years (17 to 49) and the mean follow-up was 15 months (6 to 30). Patients with hypermobility had a significant improvement in function following surgery, with reasonable rates of satisfaction, perceived improvement, willingness to repeat and likelihood of recommendation. Functional improvements were significantly less than in control patients (p < 0.01). Joint hypermobility is not a contraindication to MPFL reconstruction although caution is recommended in managing the expectations of patients with hypermobility before consideration of surgery

We report a prospective analysis of clinical outcome in patients treated with medial patellofemoral ligament (MPFL) reconstruction using an autologous semitendinosus graft. The technique includes superolateral portal arthroscopic assessment before and after graft placement to ensure correct graft tension and patellar tracking before fixation. Between October 2005 and October 2010, a total of 201 consecutive patients underwent 219 procedures. Follow-up is presented for 211 procedures in 193 patients with a mean age of 26 years (16 to 49), and mean follow-up of 16 months (6 to 42). Indications were atraumatic recurrent patellar dislocation in 141 patients, traumatic recurrent dislocation in 50, pain with subluxation in 14 and a single dislocation with persistent instability in six. There have been no recurrent dislocations/subluxations. There was a statistically significant improvement between available pre- and post-operative outcome scores for 193 patients (all p < 0.001). Female patients with a history of atraumatic recurrent dislocation and all patients with history of previous surgery had a significantly worse outcome (all p < 0.05). The indication for surgery, degree of dysplasia, associated patella alta, time from primary dislocation to surgery and evidence of associated cartilage damage at operation did not result in any significant difference in outcome.

This series adds considerably to existing evidence that MPFL reconstruction is an effective surgical procedure for selected patients with patellofemoral instability.

Introduction

Recurrent patellar dislocation is often reported in bilateral knees in young active individuals. The medial patellofemoral ligament (MPFL) tear is the attributable cause behind many of them and warrants reconstruction of the ligament to stabilize the patellofemoral joint. Besides, trochleoplasty and Fulkerson's osteotomy are some other procedures that are performed to treat this problem. This study aimed to compare the clinical and functional outcomes in a cohort of patients with single-stage bilateral realignment procedures vs staged procedures.

Aims

The Oswestry-Bristol Classification (OBC) was recently described as an MRI-based classification tool for the femoral trochlear. The authors demonstrated better inter- and intraobserver agreement compared to the Dejour classification. As the OBC could potentially provide a very useful MRI-based grading system for trochlear dysplasia, it was the aim to determine the inter- and intraobserver reliability of the classification system from the perspective of the non-founder.

The tensile strength of the medial patellofemoral ligament (MPFL), and of surgical procedures which reconstitute it, are unknown. Ten fresh cadaver knees were prepared by isolating the patella, leaving only the MPFL as its attachment to the medial femoral condyle. The MPFL was either repaired by using a Kessler suture or reconstructed using either bone anchors or one of two tendon grafting techniques. The tensile strength and the displacement to peak force of the MPFL were then measured using an Instron materials-testing machine. The MPFL was found to have a mean tensile strength of 208 N (SD 90) at 26 mm (SD 7) of displacement. The strengths of the other techniques were: sutures alone, 37 N (SD 27); bone anchors plus sutures, 142 N (SD 39); blind-tunnel tendon graft, 126 N (SD 21); and through-tunnel tendon graft, 195 N (SD 66). The last was not significantly weaker than the MPFL itself

Purpose of the study: From a biomechanical view, the medial force stabilising the patella is assured for 50 to 60% by the medial patellofemoral ligament (MPFL). The purpose of this cadaver study was to present a precise description of the anatomic features of the MPFL concerning its femoral insertion, its relations with the oblique vastus medialis (OVM) and its relation with the medial collateral ligament (MCL) in order to optimise surgical reconstruction. Material and methods: This cadaver study was performed on 23 knees from fresh cadavers. All measures were made knee flexed 30° by the same operator. Insertions of the OVM on the MPFL, when present, were identified. The length of the zone of reflexion was recorded. For these measurements, a orthonormal landmark centred on the femoral insertion of the MPFL was established. This landmark was used to position the medial epicondyle and the adductor tubercle for each knee. Results: The MPFL was found in all 23 knees (100%); the length of the MPFL was 57.7±5.8 mm; its femoral insertion measured 12.2±2.6 mm (8–136); its patellar insertion measured 24.4±4.8 mm. A junction between the OVM and the MPFL was found for all 23 knees (100%). This zone appeared to be a veritable reflexion zone with the OVM fibres arching over the MPFL fibres for a length of 25.7±6 mm. Discussion: Our study confirms the constant presence of the MPFL, observed in 100% of the knees studied. During the reconstruction of the MPFL, the key point is the position of the femoral insertion of the ligament, in order to restore the native femoral insertion of the MPFL surgically and thus attempt to recreate perfect isometry of the graft. The graft must be positions 10 mm posteriorly to the medial epicondyle and 10 mm distally to the adductor tubercle. In our cadaver the MPFL, the main medial stabilising force of the patella was a constant finding, always located in the second thickness of the medial plane of the knee. Conclusion: We detailed the native femoral insertion of the MPFL and described its relations with the medial femoral epicondyle and the adductor tubercle using an orthonormal landmark. Long-term function of the graft depends on proper positioning

Introduction. Patellar stability is an important component for a correct kinematic behaviour of the knee that depends on several factors such as joint geometry, muscles strength and soft tissues actions. Patellofemoral (PF) maltracking can results in many joint disorders which can cause pain and mobility alterations. The medial patellofemoral ligament (MPFL) is an important stabilizing structure for the patellofemoral joint. The aim of this study was to analyze patellofemoral kinematics with particular attention to the contribution of MPFL on patella stability. Methods. Using a navigation system PF kinematics during passive flexion/extension movements with quadriceps loaded at 60N, was recorded on 6 cadavers in three different anatomical conditions: intact knee, MPFL cut and MPFL reconstructed with graft. Test on patella was conducted without lateral force and with applied lateral force (25N). Tilt and lateral shift was evaluated in both cases at 0°. 30°, 60°and 90° of flexion. Results. Test results without applied force showed that there is no statistical difference between intact knee and MPFL cut conditions in all ranges of flexion, both for medio-lateral shift and tilt, which have low values. In test with applied force a significative increase of patellar lateral translation at 30° (16,8 ± 13,4 mm) and 60° (18,6 ± 6,4 mm) was found. MPFL reconstructed knee behaviour was not statistically different to intact knee both for tilt and medio-lateral shift. Therefore lateral translation was widely reduced with the graft. Conclusions. Without applied stress intact knees and MPFL cut knees behave in the same way. In applied load conditions MPFL cut knees show wide lateral translation in respect to intact and reconstructed knees. MPFL reconstructed knees are similar to intact knee therefore MPFL restraint is significant only in stress conditions. This may indicate that the MPFL is a aponeurosis, with an active role under stress, but low role during neutral knee flexion

INTRODUCTION. The medial patellofemoral ligament (MPFL) has been recognised as the most important medial structure preventing lateral dislocation or subluxation of the patella (LeGrand 2007). After MPFL rupture the patella deviates from the optimal path resulting in an altered retropatellar pressure distribution. This may lead to an early degeneration with loss of function and need for endoprosthetic joint replacement. The goal of this study was to obtain first data about retropatellar pressure distribution under simulation of physiological quadriceps muscle loading and evaluate the influence of ligament instabilities. MATERIALS AND METHOD. On ten fresh-frozen cadaveric knees the quadriceps muscle was divided into 5 parts along their anatomic fiber orientation analogous to Farahmand 1998. Muscular loading was achieved by applying weights to each of the five components in proportion to the cross sectional muscle area (total load 175 N). A custom made sensor was introduced between the patella and femur [Pliance, Novel / Germany]. The sensor consists of 85 single cells. The robot-control-unit is liked to a force-torque sensor. The force free knee-flexion-path from 0° to 90° was calculated during three “passive path” measurements. The actual measurements followed with identical parameters. At first, the retropatellar pressure distribution was recorded with intact ligaments (“native”). After cutting the MPFL the test was repeated. Then double bundle MPFL reconstruction (Schoettle 2009) was performed and the pressure distribution was obtained again. Minimum, mean and maximum pressures and forces were statistically compared in each of the three tested conditions (native Patella with intact MPFL, cut and reconstructed MPFL). We followed the hypothesis that MPFL reconstruction can restore native retropatellar pressure distribution. RESULTS. Mean retropatellar force measured in all conditions of the MPFL was 64.29 N [F. min. 0.06, F. max. 194.91, SD 66.99] N. Mean retropatellar pressure was 285.69 [P. min. 0.00, P. max. 923.64, SD 303.73] kPa. The mean retropatellar force increased with knee flexion from 35 N [0° flexion] to 75 N [90° flexion]. After cutting the MPFL mean force decreased in all degrees of flexion compared to the native state but mean pressure increased for the first 50° of flexion. Reconstruction of the MPFL did not restore native conditions. The mean pressure was only 3 N above the one of the cut MPFL. Regarding the entire retropatellar surface, maximum pressure decreased with increasing degrees of flexion from 330 kPa to 275 KPa. After cutting the MPFL, maximum pressure decreased about 60 kPa. MPFL reconstruction resulted in an increased maximum pressure (+ 10 kPa) in all degrees of flexion, but the values of the native state could not be achieved. To our knowledge this is the first experimental data of dynamic retropatellar pressure measurements on human cadaver knees in which a force free knee flexion is performed by an industrial robot under muscular quadriceps loading. There were no significant changes in retropatellar pressures after cutting the MPFL. In contrast to our hypothesis, MPFL reconstruction does not restore native conditions at this experimental setting

Introduction. As intra-operative fluoroscopic identification of the isometric MPFL attachment to the femur can be imprecise and laborious in a surgical setting, we used clinical criteria to identify the isometric point and then studied post-operative radiographs to find out whether it was achieved and compared it with functional outcome. Materials and Methods. Sixteen patients underwent 17 MPFL reconstructions using autologous semi-tendinosis tendon graft. Clinical judgement was used to identify the optimal point for femoral attachment of the MPFL without fluoroscopy control. Post-operative radiographs at 2 weeks were analysed to confirm whether an isometric point for the reconstructed MPFL was achieved by dividing the distal femur into 4 quadrants by 2 lines on the lateral radiograph. Telephonic interview was conducted to assess functional scores using the Kujala score at a mean follow-up of 13 months. Results. In only 4 of the 17 cases, the femoral point of attachment lay in the radiographically isometric (antero-proximal) quadrant. In 8 of 17 knees, the point of MPFL attachment lay in the antero-distal quadrant. However, there was an improvement in the functional score in 14 of 16 patients, with none reporting recurrence of patellar instability. The position of the reconstructed MPFL did not correlate with functional score. Conclusion. Over-reliance on a clinical method alone for identification of the optimal point for MPFL attachment without an intra-operative radiograph leads to radiographically non-isometric positioning in a majority of cases. In the clinical setting, however, this does not correlate with adverse functional outcome, although intra-operative fluoroscopy may improve the anatomical isometry, and we therefore suggest the use of a qualitative clinical method to achieve optimal

We sought to identify the tensile properties of the medial patellofemoral ligament (MPFL), and determine whether its repair was sufficient as a means of restoring stability after acute lateral patella dislocation. We also sought to establish whether there was a correlation between the tensile properties of the anterior cruciate ligament (ACL) and the MPFL. 16 hind limbs of Merino Wethers were obtained and stored fresh frozen. The specimens were thawed overnight, dissected out and then placed in a water bath at 37 degrees centigrade for 30 minutes prior to testing. All testing was carried out in the water bath to approximate a more physiological environment. For each specimen the ACL was first tested to failure on an Instron 8511. The MPFL was then tested to failure, then repaired and retested to failure. Finally a reconstruction was carried out, using a flexor tendon, which was again tested to failure. Results:. There was no correlation between ACL and MPFL strength (p=0.677). Statistical analysis showed that the intact MPFL was significantly stronger than the repaired MPFL (P=0.001) but no different to the reconstructed MPFL (P=0.224), with no difference between repaired and reconstructed (P=0.174). A Power analysis showed that there was not adequate power to detect a significant difference between the last two pairs, and that we would have needed over 35 specimens to show a difference. This study does not support carrying out a repair of the MPFL following an acute lateral patella dislocation, as it does not restore its tensile properties. It further suggests that a reconstruction may better restore the tensile properties of this ligament

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

The medial patellofemoral ligament is commonly torn in first patella dislocation and according to the literature occurs most frequently at the femoral insertion. As research has demonstrated the MPFL to be a primary soft tissue stabilizer of the patella there has been increased interest in acute repair of the ligament with the aim of reducing the risk of recurrent dislocation. MRI is generally used pre op to identify the site of rupture allowing planning of the surgical repair, however there is currently no published data regarding the correlation between surgical and MRI findings to confirm the reliability of this modality of imaging. A retrospective analysis of all patients who were referred for MRI following patella dislocation was performed. The surgical and MRI findings of those who subsequently underwent MPFL repair were compared to look for any correlation. 41 patients were first time patella dislocators and 38 had MPFL rupture diagnosed on MRI. Of these 19 progressed to surgical intervention and 17 had adequate data available from the notes and to permit comparison. All of the MPFLs ruptured at the patella insertion. In 76.5% (13/17) of patients the site of MPFL rupture was correctly identified on MRI scan. Of those that were discordant 3/4 had the site of rupture identified as the femoral insertion on MRI and on 1/4 the MRI suggested rupture at both the femoral and patella insertions. MPFL rupture is common in first time dislocations occurring in 93%% of this cohort. There was a clear predominance patella insertion rupture in our study which contrasts with the majority of the published literature. By correlating surgical and radiological findings we can conclude that while MRI can accurately diagnose MPFL rupture at the patella insertion but it is less accurate in identifying rupture at the femoral insertion

Abstract. Patellofemoral Arthroplasty (PFA) is an alternative to TKA for patellofemoral osteoarthritis that preserves tibiofemoral compartments. It is unknown how implant positioning affects biomechanics, especially regarding the patella. This study analysed biomechanical effects of femoral and patellar component position, hypothesising femoral positioning is more important. Nine cadaveric knees were studied using a repeated-measures protocol. Knees were tested intact, then after PFA implanted in various positions: neutral (as-planned), patellar over/understuffing (±2mm), patellar tilt, patellar flexion, femoral rotation, and femoral tilt (all ±6°). Arthroplasties were implemented with CT-designed patient-specific instrumentation. Anterior femoral cuts referenced Whiteside's line and all femoral positions ensured smooth condyle-to-component transition. Knee extension moments, medial patellofemoral ligament (MPFL) length-change, and tibiofemoral and patellofemoral kinematics were measured under physiological muscle loading. Data were analysed with one-dimensional statistical parametric mapping (Bonferroni-Holm corrected). PFA changed knee function, altering extension moments (p<0.001) and patellofemoral kinematics (p<0.05), but not tibiofemoral kinematics. Patellar component positioning affected patellofemoral kinematics: over/understuffing influenced patellar anterior translation and the patellar tendon moment arm (p<0.001). Medially tilted patellar cuts produced lateral patellar tilt (p<0.001) and vice versa. A similar inverse effect occurred with extended/flexed patellar cuts, causing patellar flexion and extension (p<0.001), respectively. Of all variants, only extending the patellar cut produced near-native extension moments throughout. Conversely, the only femoral effect was MPFL length change between medially/laterally rotated components. PFA can restore native knee biomechanics. Provided anterior femoral cuts are controlled and smooth condyle-to-component transition assured, patellar position affects biomechanics more than femoral, contradicting the hypothesis

Patellar instability most frequently presents during adolescence. Congenital and infantile dislocation of the patella is a distinct entity from adolescent instability and measurable abnormalities may be present at birth. In the normal patellofemoral joint an increase in quadriceps angle and patellar height are matched by an increase in trochlear depth as the joint matures. Adolescent instability may herald a lifelong condition leading to chronic disability and arthritis. Restoring normal anatomy by trochleoplasty, tibial tubercle transfer or medial patellofemoral ligament (MPFL) reconstruction in the young adult prevents further instability. Although these techniques are proven in the young adult, they may cause growth arrest and deformity where the physis is open. A vigorous non-operative strategy may permit delay of surgery until growth is complete. Where non-operative treatment has failed a modified MPFL reconstruction may be performed to maintain stability until physeal closure permits anatomical reconstruction. If significant growth remains an extraosseous reconstruction of the MPFL may impart the lowest risk to the physis. If minor growth remains image intensifier guided placement of femoral intraosseous fixation may impart a small, but acceptable, risk to the physis. This paper presents and discusses the literature relating to adolescent instability and provides a framework for management of these patients. Cite this article: Bone Joint J 2017;99-B:159–70

Aim. This study looks for correlation between pre-operative MRI and intra-operative surgical findings regarding the site of medial patellofemoral ligament (MPFL) rupture in first time patella dislocaters with the aim of confirming the reliability of this modality of imaging. Methods. A retrospective analysis of all patients who were referred for MRI following patella dislocation was performed. The surgical and MRI findings of those who subsequently underwent MPFL repair were compared to look for any correlation. Results. 41 patients were first time patella dislocators and 38 had MPFL rupture diagnosed on MRI. Of these 19 progressed to surgical intervention and 17 had adequate data available from the notes to permit comparison. All of the MPFLs ruptured at the patella insertion. In 76.5% (13/17) of patients the site of MPFL rupture was correctly identified on MRI scan. Of those that were discordant, 3/4 had the site of rupture identified as the femoral insertion on MRI and on 1/4 had an MRI suggestive of rupture at both the femoral and patella insertions. Conclusion. MPFL rupture is common in first time dislocations occurring in 93% of this cohort on MRI. There was a predominance for patella insertion rupture in our study which contrasts with the majority of the published literature. By correlating surgical and radiological findings we can conclude that while MRI can accurately diagnose MPFL rupture at the patella insertion it is less accurate in identifying rupture at the femoral insertion

Purpose of Study: The role of surgery in the treatment of acute patella dislocation has always been controversial with procedures falling in and out of popularity. Since the Medial Patellofemoral ligament was first described in 1979, its importance as a prime patella stabiliser has been defined, and procedures for its repair and reconstruction have been described. We believe that the MPFL has a pivotal role in the stability of the patella, and is disrupted in all patients with acute patella dislocation. Failure to address this will inevitably lead to ongoing patellofemoral symptoms. Methods: We summarise the current literature detailing the anatomy and biomechanical properties of the native as well repaired MPFL. We present our own experience of treating acute patella dislocations by repair of the Medial Patellofemoral Ligament, in acute cases. A lesion can occur anywhere along its length from the superomedial patella to a point superoposterior to the adductor tubercle. The technique of repair has to address the site of primary disruption, as well as any associated intraarticular knee injuries. Results: In one series we have shown that of 13 patients who presented with acute patella dislocation, 10 had an MRI proven lesion of the MPFL and went on to have an open repair which reconstituted patella stability. Conclusion: A lesion of the MPFL is the primary pathology in acute patella dislocation, and we believe that this lesion warrants surgical intervention to avoid progressive symptoms