Accuracy of femoral tunnel placement in medial patellofemoral ligament reconstruction: the effect of a nearly true-lateral fluoroscopic view

Lateral to medial fluoroscopic view improves the accuracy of identifying the MPFL femoral footprint using Schottle's technique

PURPOSE

This study investigated the effect of different fluoroscopy settings on the accuracy of locating Schottle's point during medial patellofemoral ligament (MPFL) reconstruction.

METHODS

The centre of the MPFL femoral footprint was identified and marked on 44 dry femurs. Two standard true lateral knee fluoroscopic images were obtained: (1) medial to lateral (ML) and (2) lateral to medial (LM). The deviation between the anatomically determined MPFL femoral footprint and the fluoroscopically identified point was measured on both fluoroscopic images. An 'acceptable tunnel location' was defined as within a 5- or 7-mm margin of error from the anatomic MPFL footprint. Distal femoral morphometric dimensions were also measured using digital calipers. Statistical analysis determined discrepancies between techniques and their relation to femoral morphometry.

RESULTS

The LM view yielded a significantly smaller distance between the anatomical MPFL footprint and Schottle's point compared to the ML view (3.2 ± 1.5 vs. 4.5 ± 2.1 mm, p < 0.001). The LM view achieved acceptable tunnel locations, meeting the 5-mm error criterion in 90.9% of cases, while the ML view achieved 65.9% (p < 0.001). Both views yielded acceptable tunnel locations at similar rates using the 7-mm error criterion (n.s.). The anatomic MPFL footprint was displaced towards the anterior and proximal location in the ML view in reference to the Schottle point. No correlation was observed between any of the morphometric measurements and the deviations.

CONCLUSIONS

This study demonstrated that using the LM fluoroscopic view improves the accuracy of femoral tunnel placement when identifying the MPFL footprint via the Schottle technique. Adopting the LM view in surgical practice will help surgeons locate the anatomical femoral footprint accurately, replicating the native MPFL and enhancing clinical outcomes.

LEVEL OF EVIDENCE

Level 4, cadaveric study.

Palpation and fluoroscopy are valid but unreliable for the assessment of femoral tunnel position after medial patellofemoral ligament reconstruction

OBJECTIVES

The purpose of this study was to evaluate the validity and reliability of two techniques, palpation and fluoroscopy, for assessing medial patellofemoral ligament (MPFL) reconstruction femoral tunnel position accuracy.

METHODS

Twenty-one fresh frozen cadaveric knees had an MPFL femoral tunnel drilled and filled with a metal screw. Tunnels were created in a nonstandard fashion to ensure the sample included a range of tunnel positions from poor to ideal. Six experienced sport medicine and arthroscopy surgeons evaluated the placement of the femoral tunnel by palpating the screw in relation to anatomic landmarks and by fluoroscopy related to Schöttle's Point. They evaluated 1) the accuracy of femoral tunnel placement, 2) the direction of tunnel error, and 3) the clinical acceptability of the tunnel position. Validity measures included sensitivity, specificity, and correlation to clinical acceptability, which were calculated for the palpation and fluoroscopic assessments. Reliability measures included interrater reliability (ICC 2,k) for femoral tunnel accuracy and percent agreement of the raters' tunnel direction assessment.

RESULTS

The palpation method demonstrated a sensitivity of 0.79 and specificity of 0.84 for assessing the accuracy of femoral tunnel placement, while the fluoroscopic method showed a sensitivity of 0.83 and specificity of 0.92. Pearson correlation coefficients for clinical acceptability of tunnel position were high, with both techniques ranging from .589 to .854. Interrater reliability for the palpation and fluoroscopic techniques for assessment of tunnel accuracy were 0.31 and 0.55 (ICC 2,k), respectively. Assessment of the direction of tunnel error was good with the fluoroscopic technique slightly more accurate than palpation.

CONCLUSION

This study demonstrated that both palpation and fluoroscopy are valid techniques for assessing femoral tunnel position after MPFL reconstruction. Despite demonstrating good validity, the accuracy of assessing tunnel position was unreliable in a group of six experienced knee surgeons. Further research into MPFL reconstruction femoral tunnel assessment techniques, including patient-specific reference standards, is warranted.

LEVEL OF EVIDENCE

Level 2.

Radiographic Landmark Measurements for the Femoral Footprint of the Medial Patellofemoral Complex May Be Affected by Visible Femoral Shaft Length on Lateral Knee Radiographs

PURPOSE

To assess the effect of visible femoral shaft length on the accuracy of radiographic landmarks of the medial patellofemoral complex (MPFC).

METHODS

In 9 cadaveric knees, the MPFC footprint was exposed on the medial femur, and its proximal and distal boundaries were marked. Lateral fluoroscopic images of the knee were assessed in 1-cm length increments, beginning 1 cm proximal to the medial condyle and continuing proximally to 8 cm. The MPFC midpoint was described on each image relative to the posterior cortical line of the femur and a line perpendicular to this line through the proximal margin of the medial condyle. In addition, the MPFC midpoint was assessed relative to a line from the proximal posterior cortex to the midpoint of Blumensaat line.

RESULTS

Using the posterior cortical line as a reference, the MPFC radiographic landmark moved anteriorly with decreasing visible femoral shaft on radiographs, particularly at 4 cm and less. However, no proximal-distal change was noted. Linear regression analysis demonstrated a relationship between visible femoral shaft and MPFC position on radiographs (R = 0.461, R2 = 0.212, B = -0.636, P < .001). For every centimeter decrease in the visible femoral shaft, the radiographic MPFC footprint moved anteriorly by 0.636 mm. Receiver operating characteristic curve analysis revealed that a minimum of 4 cm of femoral shaft on lateral radiographs is required for accurate MPFC footprint localization (area under the curve = 0.80; sensitivity = 76.7%; specificity = 69.0%; P < .001). In contrast, no anterior-posterior change was seen when referencing a line from the proximal posterior cortex to the midpoint of Blumensaat line.

CONCLUSIONS

When using the posterior cortical line to identify the midpoint of the MPFC, at least 4 cm of femoral shaft should be visible for accurate assessment. If less than 4 cm of shaft is visible, a line through the midpoint of Blumensaat line and the proximal posterior cortex can be used as an alternative method to estimate the position of the femoral footprint.

CLINICAL RELEVANCE

As fluoroscopy is frequently used intraoperatively for MPFC reconstruction, our findings may serve as a guide when assessing femoral tunnel placement on fluoroscopy.

Comparison of five different fluoroscopic methods for identifying the MPFL femoral footprint

PURPOSE

The success of medial patellofemoral ligament (MPFL) reconstruction is closely linked to the precise positioning of the femoral tunnel. Intraoperative fluoroscopy is commonly utilized to identify the MPFL footprint. This study aimed to ascertain the most accurate fluoroscopic method among the five previously described methods used to determine the MPFL femoral footprint.

MATERIALS AND METHODS

Using 44 well-preserved dry femur bones, the MPFL femoral insertion site was demarcated using anatomical bony landmarks, namely the center of the saddle sulcus between the medial epicondyle, adductor tubercle and gastrocnemius tubercle. Fluoroscopic true lateral knee images were acquired and measurements taken, referencing established methods by Schottle et al., Redfern et al., Wijdicks et al., Barnett et al., and Kaipel et al. The distance between anatomic and fluoroscopic MPFL footprints was then measured on digital fluoroscopic images. The accuracy of the locations was compared using a margin of error of 5 and 7 mm.

RESULTS

The Schottle method consistently emerged superior, showcasing the smallest mean distance (3.2 ± 1.2 mm) between the anatomic and radiographic MPFL footprints and a high in-point detection rate of 90.9% under 5 mm criteria. While the Redfern method displayed perfect accuracy (100%) within the 7 mm criteria, the Schottle method also performed 97.7% accuracy.

CONCLUSIONS

For intraoperative identification of the MPFL footprint using fluoroscopy, the Schottle method is the most consistent and accurate among the assessed methods. Thus, its accuracy in detecting the MPFL footprint makes it recommended for MPFLR to ensure optimal outcomes.

LEVEL OF EVIDENCE

Level IV, cadaveric study.

MPFL reconstruction with proximal rather than distal femoral tunnel position leads to less favorable short-term results

BACKGROUND

This study aimed to compare the clinical and radiological outcomes of medial patellofemoral ligament (MPFL) reconstruction (MPFLR) between anatomic femoral tunnel positions: proximal (near adductor tubercle [AT]) and distal (near medial epicondyle [ME]).

HYPOTHESIS

MPFLR with the proximal femoral tunnel position has worse clinical and radiological outcomes than those with the distal femoral tunnel position.

PATIENTS AND METHODS

Fifty-five patients who underwent isolated MPFLR with proximal or distal femoral tunnels with at least 2 years of follow-up were retrospectively analyzed. Based on postoperative CT images, 28 patients were classified as group AT and the remaining 27 patients were classified as group ME. The International Knee Documentation Committee, Lysholm, Tegner, Kujala scores, and complications were evaluated. Radiologically, the Caton-Deschamps Index (CDI), patellar tilt angle, patellofemoral osteoarthritis (PFOA), patellofemoral cartilage status by the International Cartilage Repair Society (ICRS) grade, bone contusion, and MPFL graft signal intensity were evaluated.

RESULTS

All clinical scores significantly improved in both groups (p<0.01). No statistically significant difference was noted between the two groups in regards to their preoperative demographic data, postoperative clinical scores, complications, or radiological findings (CDI, patellar tilt angle, PFOA, bone contusion, and graft signal intensity). The group AT had worse cartilage status on the medial facet of the patella (p=0.02). The ICRS grade for the medial facet of the patella statistically progressed in group AT compared to group ME (p=0.04) as well.

DISCUSSION

Both groups showed significantly improved clinical outcomes. However, for the medial facet of the patella, MPFLR with the proximal femoral tunnel position had worse cartilage status and ICRS grade progression than those with the distal femoral tunnel position.

LEVEL OF EVIDENCE

III; retrospective comparative study.

A Novel Technique of Arthroscopic Femoral Tunnel Placement during Medial Patellofemoral Ligament Reconstruction for Recurrent Patellar Dislocation

Recurrent patellar dislocation is a commonly encountered patellofemoral disease. Prompt surgical intervention is indicated for recurrent dislocation to restore patellofemoral stability. As one of the most preferred procedures, medial patellofemoral ligament (MPFL) reconstruction has been implemented on a large scale. Femoral tunnel placement remains a crucial technical issue during MPFL reconstruction and is critical to ensure the isometry and proper tension of the graft. Currently, visual-palpatory anatomic landmarks and fluoroscopy-guided radiographic landmarks comprise the main approaches to intraoperative femoral tunnel positioning. However, the accuracy of both methods has been questioned. This article introduces an arthroscopic femoral tunnel placement technique. Apart from traditional anteromedial and anterolateral portals, two auxiliary arthroscopic portals are specially designed. The adductor tubercle, the medial epicondyle and the posterior edge are selected as main anatomic landmarks and are directly visualized in sequence under arthroscope. The relative position between the femoral attachment of the MPFL and the three landmarks is measured on preoperative three-dimensional computed tomography, providing semi-quantified reference for intraoperative localization. This technique achieves minimally invasive tunnel placement without X-ray exposure, and especially suits obese patients for whom palpatory methods are difficult to perform.

Accuracy of femoral tunnel positioning in medial patellofemoral ligament reconstruction: anatomic insertion leads to better clinical outcome

PURPOSE

The medial patello-femoral ligament (MPFL) is considered the primary restraint against patellar dislocation and its reconstruction is indicated in recurrent patellar instability. An anatomical positioning of MPFL femoral insertion is recommended to achieve satisfactory clinical outcomes and prevent osteoarthritis (OA) due to an altered kinematics. The purpose of the study was first to assess the relationship between correct femoral tunnel position and better clinical outcomes and lower patellofemoral osteoarthritis rate. Second, correlation of outcomes with factors potentially affecting the results, such as the type of graft, patellar height and trochlear dysplasia.

METHODS

Fifty-three patients (58 knees) who underwent MPFL reconstruction between 2009 and 2018 by a senior knee surgeon were retrospectively evaluated. Knee radiographs were performed before surgery, 12 months later and at last follow-up to assess trochlear dysplasia, patellar height and patellofemoral OA. The tibial tuberosity-trochlear groove (TT-TG) value was measured on a CT scan. The accuracy of graft positioning was evaluated on sagittal radiographs according to Schöttle et al. Subjective outcomes were collected before surgery, at 12 months and at last follow-up using several validated scores.

RESULTS

Forty-six patients (51 knees) with a mean age of 24.1 ± 7.4 years were included in the study. Mean follow-up was 8.9 ± 2.1 years. A significant improvement in all clinical scores was observed at 12 months and final follow-up. Anatomic Insertion (AI) of reconstructed MPFL was considered optimal in 33 (64.7%) and sub-optimal in 18 (35.3%) patients. Sub-optimal AI resulted in lower Kujala, IKCD and higher VAS score (p < 0.01); moreover, for every 1 mm distance in any direction from the ideal insertion, a decrease of 0.8 [95% CI (-1.4; -0.2)] in Kujala score and 0.8 [95% CI (-1.3; -0.3)] in IKDC was observed. At final follow-up, 8 patients presented patellofemoral OA Iwano grade 3 (15.7%): although that incidence did not correlate to graft positioning, the use the artificial ligament in all these cases appeared to be significant.

CONCLUSION

The present study confirms the importance of an optimal anatomic femoral insertion in MPFL reconstruction, reporting a significant positive correlation between graft positioning and clinical outcome. No significant correlations were found between anatomic insertion and patello-femoral OA development.

LEVEL OF EVIDENCE

IV.

Influence of the Fluoroscopy Setting towards the Patient When Identifying the MPFL Insertion Point

(1) The malposition of the femoral tunnel in medial patellofemoral ligament (MPFL) reconstruction can lead to length changes in the MPFL graft, and an increase in medial peak pressure in the patellofemoral joint. It is the cause of 36% of all MPFL revisions. According to Schöttle et al., the creation of the drill canal should be performed in a strictly lateral radiograph. In this study, it was hypothesized that positioning the image receptor to the knee during intraoperative fluoroscopy would lead to a relevant mispositioning of the femoral tunnel, despite an always adjusted true-lateral view. (2) A total of 10 distal femurs were created from 10 knee CT scans using a 3D printer. First, true-lateral fluoroscopies were taken from lateral to medial at a 25 cm (LM25) distance from the image receptor, then from medial to lateral at a 5 cm (ML5) distance. Using the method from Schöttle, the femoral origin of the MPFL was determined when the femur was positioned distally, proximally, superiorly, and inferiorly to the image receptor. (3) The comparison of the selected MPFL insertion points according to Schöttle et al. revealed that the initial determination of the point in the ML5 view resulted in a distal and posterior shift of the point by 5.3 mm ± 1.2 mm when the point was checked in the LM25 view. In the opposite case, when the MPFL insertion was initially determined in the LM25 view and then redetermined in the ML5 view, there was a shift of 4.8 mm ± 2.2 mm anteriorly and proximally. The further positioning of the femur (distal, proximal, superior, and inferior) showed no relevant influence. (4) For fluoroscopic identification of the femoral MPFL, according to Schöttle et al., attention should be paid to the position of the fluoroscopy in addition to a true-lateral view.

Application of a true lateral virtual radiograph from 3D-CT to identify the femoral reference point of the medial patellofemoral ligament

PURPOSE

The purpose of this study is two-fold: (1) to describe the femoral reference point of the medial patellofemoral ligament (MPFL) on a virtual true lateral radiograph reconstructed from a three-dimensional computed tomography (3D-CT) image and (2) to compare this point with that of patients without patellofemoral instability and with Schöttle's point.

METHODS

A total of 26 consecutive patients (29 affected knees) with recurrent patellar dislocation (RPD), who underwent MPFL reconstruction were included in this study (4 males; 22 females; mean age, 24.0 years old). Using a true lateral 3DCT image, the MPFL femoral insertion was identified and marked with a 2-mm circle, and this image was reconstructed as a virtual true lateral radiograph. Following Schöttle's method, the point of intersection was described by their anterior-posterior and proximal-distal positions. As a control population, 29 age- and gender-matched patients with anterior cruciate ligament (ACL) injuries were also analysed.

RESULTS

The points in RPD patients were located significantly posterior (-2.5 ± 2.3 mm, p < 0.01) to the line representing an extension of the posterior cortex of the femur and distal (- 6.9 ± 2.4 mm, p < 0.01) to the posterior origin of the medial femoral condyle compared with those in the control population. The mean reference point of RPD patients was located in a 3.8-mm posterior and 4.4-mm distal position compared with Schöttle's point.

CONCLUSIONS

An anatomical and radiographic femoral reference point of the MPFL on a true lateral virtual radiograph was described with our method. In patients with RPD, this reference point was identified to be more posterior and distal to Schöttle's point. More anatomical and individualized MPFL reconstruction will be secured using our method.

LEVEL OF EVIDENCE

Level IV.

Using Anatomic Landmarks to Locate Schöttle's Point Was Accurate Without Fluoroscopy During Medial Patellofemoral Ligament Reconstruction

PURPOSE

The purpose of the present study was to analyze the anatomic landmarks of Schöttle's point and establish a locating method for identification.

METHODS

From 2013 to 2016, patients undergoing medial patellofemoral ligament (MPFL) reconstruction for patellofemoral instability were enrolled.

INCLUSION CRITERIA

at least 2 episodes of patellar dislocation.

EXCLUSION CRITERIA

previous knee surgeries, open physes, severe trochlear dysplasia， tibial tuberosity lateralization, or patella alta. Group A: From January 2013 to December 2013, preoperative 3-dimensional computed tomography (3D-CT) images were obtained. Anatomic features of Schöttle's point were measured on the 3D-CT images. A Schöttle's point locating method with 2 distinct landmarks was established. Group B: From January 2014 to January 2016, consecutive MPFL reconstructions were performed. The placement of Schöttle's point was following the established method without fluoroscopy. The accuracy of femoral tunnel positions was assessed on the 3D-CT images postoperatively.

RESULTS

CT images of 53 knees were obtained in group A. Forty-seven MPFL reconstructions were performed in group B. No significant difference was found between the 2 groups regarding to demographic characteristics. The intraclass correlation coefficients were excellent for all measures (r = 0.97). In group A, Schöttle's point was 8.1 ± 0.2 mm (95% confidence interval [CI], 7.7-8.5) distal to the apex of the adductor tubercle and 8.0 ± 0.3 mm (95% CI, 7.4-8.6) anterior to the posterior edge. Apex of the adductor tubercle was defined as the most convex point, and posterior edge was defined as the edge of the posteromedial cortex in the transition area between the medial condyle and femoral shaft. In group B, 44 of 47 femoral tunnels (93.6%) were considered localized in the proper zone.

CONCLUSIONS

Schöttle's point was approximately 8 mm distal to the apex of the adductor tubercle and 8 mm from the posterior edge. Schöttle's point locating method without fluoroscopy had high accuracy.

LEVEL OF EVIDENCE

Level IV, case series.

[Research progress in femoral tunnel positioning points of medial patellofemoral ligament reconstruction]

Objective

To review the research progress of location methods and the best femoral insertion position of medial patellofemoral ligament (MPFL) reconstruction of femoral tunnel, and provide reference for surgical treatment.

Methods

The literature about femoral insertion position of the MPFL reconstruction in recent years was extensively reviewed, and the anatomical and biomechanical characteristics of MPFL, as well as the advantages and disadvantages of femoral tunnel positioning methods were summarized.

Results

The accurate establishment of the femoral anatomical tunnel is crucial to the success of MPFL reconstruction. At present, there are mainly two kinds of methods for femoral insertion: radiographic landmark positioning method and anatomical landmark positioning method. Radiographic landmark positioning method has such advantages as small incision and simple operation, but it can not be accurately positioned for patients with severe femoral trochlear dysplasia. It is suggested to combine with the anatomical landmark positioning method. These methods have their own advantages and disadvantages, and there is no unified positioning standard. In recent years, the use of three-dimensional design software can accurately assist in the MPFL reconstruction, which has become a new trend.

Conclusion

Femoral tunnel positioning of the MPFL reconstruction is very important. The current positioning methods have their own advantages and disadvantages. Personalized positioning is a new trend and has not been widely used in clinic, its effectiveness needs further research and clinical practice and verification.

Radiographic Reference Points Do Not Ensure Anatomic Femoral Fixation Sites in Medial Patellofemoral Ligament Reconstruction: A Quantified Anatomic Localization Method Based on the Saddle Sulcus

BACKGROUND

Medial patellofemoral ligament (MPFL) reconstruction is one of the main treatments for lateral patellar translation. Based on intraoperative true lateral radiographs, the accepted methods for femoral MPFL tunnel location are potentially inaccurate. Direct assessment of anatomic characteristics during surgery through palpation of the anatomic landmarks involving the saddle sulcus might help eliminate tunnel malposition.

HYPOTHESIS

The saddle sulcus is a reliable osseous landmark where the MPFL attaches for tunnel placement.

STUDY DESIGN

Descriptive laboratory study.

METHODS

A total of 9 fresh-frozen unpaired human cadaveric knees were dissected; MPFL insertion point and relative osseous structures were marked. Three-dimensional images and transformed true lateral radiographs were obtained for analysis; 3 previously reported radiographic reference points for MPFL femoral tunnel placement were determined on all images and compared with the anatomic insertion.

RESULTS

A saddle sulcus consistently existed where the MPFL was attached, located at 11.7 ± 5.9 mm from the apex of the adductor tubercle (AT) to the medial epicondyle (ME), 62.8% of the average distance between the apexes of the AT and ME, and 5.6 ± 2.8 mm perpendicular-posterior to the border connecting the AT and ME. The reported radiographic reference points were located at average distances of 6.2 ± 3.2 mm (Schöttle method), 5.9 ± 2.3 mm (Redfern method), and 7.3 ± 6.6 mm (Fujino method) from the saddle sulcus center on the true lateral radiographs.

CONCLUSION

The saddle sulcus was a reliable landmark where the MPFL was anatomically attached, located approximately 12 mm from the AT to the ME (approximately 60% along a line from the AT to the ME) and 6 mm perpendicular-posterior to the border connecting the apexes of the AT and ME. Additionally, the saddle sulcus position presented variability on the femoral aspect of different knees. All of the average direct distances from the sulcus to the reference radiographic points exceeded 5 mm, and tunnel localizations on a true lateral radiograph were inaccurate.

CLINICAL RELEVANCE

This study demonstrates the potential precise position of the saddle sulcus, according to the ME and AT, as a reliable anatomic landmark for MPFL femoral tunnel location. Radiographic reference points were not accurate during MPFL reconstruction. Direct palpation of the landmarks might be effective for femoral MPFL tunnel placement.

Patient-Reported Outcomes After Revision Surgery for Failed Medial Patellofemoral Ligament Reconstruction: A Matched-Pair Analysis Including Correction of Predisposing Factors

BACKGROUND

Complications and the need for revision surgery after medial patellofemoral ligament reconstruction (MPFLR) are evident in the current literature. However, there is a shortage of clinical data evaluating the results of revision surgery in individual patients after failed MPFLR.

PURPOSE

To investigate the results of tailored revision surgery for failed MPFLR, including the correction of predisposing factors.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Between August 2015 and March 2019, 25 patients (male:female, n = 9:16; mean ± SD age, 25.9 ± 6.5 years) underwent revision surgery for failed MPFLR (study group). The Banff Patella Instability Instrument 2.0 (BPII 2.0) and a numerical analog scale (0-10) for patellofemoral pain and subjective knee joint function were used to assess patient-reported quality of life before and after revision surgery. The control group of 50 patients (male:female, n = 18:32; age, 22.8 ± 4.3 years) who underwent identical patellar-stabilizing procedures was matched 1:2 by the surgical procedure, predisposing factors, sex, age, and follow-up time.

RESULTS

Evaluation was performed postoperatively at a mean 27.8 ± 14.0 months (range, 12-54 months) in the study group and 26.1 ± 11.2 months (range, 12-56 months) in the control group (P = .55). The BPII 2.0 score increased from 28.6 ± 17.9 points to 68.7 ± 22.3 points (P < .0001) in the study group and from 43.8 ± 22.5 points to 75.5 ± 21.4 points (P < .0001) in the control group from preoperatively to postoperatively, respectively. Before revision surgery, the BPII 2.0 scores in the study group were significantly inferior to those in the control group (P = .0026). At the final follow-up, the BPII 2.0 score in the study group was not significantly lower (P = .174), and a similar number of patients in the study group and the control group achieved the minimally clinically important difference (P = .49). Patellofemoral pain and subjective knee joint function improved significantly in both groups (P < .0001, P < .0001), without any significant difference between them at the final follow-up (P = .85, P = .86).

CONCLUSION

Revision surgery for MPFLR failure, including the correction of major anatomic risk factors, yielded a significant improvement in patient-reported quality-of-life outcome measures. Patients with failed MPFLR, however, were significantly more restricted before revision surgery than patients without previous interventions when evaluated with the BPII 2.0.

Comparative Analysis of Sagittal-Plane Radiographic Landmarks Used to Identify the Femoral Attachments of Lateral Knee Structures

PURPOSE

To compare previously described radiographic parameters for the localization of the lateral knee (LK) structures, including the popliteal tendon (Pop), anterolateral ligament (ALL), and lateral collateral ligament (LCL), to determine which method best estimates the femoral attachment of each LK structure.

METHODS

Twenty-nine human cadaveric knee specimens were carefully dissected to identify the LCL, ALL, and Pop. The femoral attachment for each structure was labeled with a radiopaque bead. LK radiographic images were obtained using fluoroscopy. Two radiographic approaches were used to identify each LK structure (Pop-A, Pop-B, LCL-A, LCL-B, ALL-A, and ALL-B) via previously published methods based on radiographic landmarks including the posterior femoral cortex and the Blumensaat line. The identification of radiographic landmarks was performed at 2 different time points by 2 different surgeons to determine the Pearson correlation between values, as well as interobserver and intraobserver reliability and reproducibility. The paired t test was conducted to compare the distance between the actual attachment site (as determined by the bead location) and the 2 radiographically identified estimations of attachment locations.

RESULTS

For the LCL, the mean difference between the actual location and the estimated location via application of the LCL-B method (5.0 ± 2.4 mm) was significantly less than that estimated using the LCL-A method (8.2 ± 3.3 mm, P < .0001). Likewise, the Pop-B (5.7 ± 2.0 mm) and ALL-B (9.3 ± 4.5 mm) methods were shown to have smaller differences between the actual and estimated femoral attachment sites of the Pop insertion and ALL insertion, respectively (P < .0001). Methods for estimating the ALL femoral origin were the worst among the LK structures analyzed, with 90% of estimated values greater than 5 mm from the anatomic origin. Interobserver and intraobserver intraclass correlation coefficients were 0.785 or higher.

CONCLUSIONS

Previously described radiographic methods for localization of the femoral attachment sites of the LK structures resulted in estimated locations that were significantly different from the locations of the radiographic beads placed at the anatomic femoral attachment sites of these structures. Therefore, radiographic methods used to localize the femoral attachments of the LK structures may not be reliable.

CLINICAL RELEVANCE

This study shows the variability of the anatomy of the LK structures and the lack of reproducible radiographic criteria to identify these structures. As a result, there will be decreased reliance on radiographic landmarks to identify the placement of femoral grafts and fixation when reconstructing these structures.

Anatomical femoral tunnel positioning in the medial patellofemoral ligament reconstruction: is the free-hand technique accurate?

Background

During medial patellofemoral ligament (MPFL) reconstruction, achieving anatomical positioning of the femoral and patellar origins is important for restoration of patellofemoral biomechanics. Although visual and manual detection can also be used to determine the femoral point of the MPFL, minimal research exists regarding accuracy of this method. Our aim was to evaluate the accuracy of free-hand method in determining the femoral point of the MPFL during surgery.

Methods

A prospective analysis was completed with 19 patients (20 knees), age ranging 15 to 39 years, in whom, three orthopedic surgeons with experience in knee procedures performed surgical reconstruction of the MPFL. MPFL femoral origin was accessed in a free-hand technique and a strict lateral view of the knee was then obtained. If the selected point was not considered appropriate, a better position was identified following the criteria set forth by Schottle.

Results

In a mean clinical follow-up of 2.3±1.3 years, anatomical point was achieved using the free-hand palpation method in seven knees (28.5%). Among the thirteen knees for whom the anatomical point was not attained without fluoroscopy, the mean error pattern found was 27.5%±8.6% for proximal (P-D axis) and 24%±6.3% for anterior in the posterior-anterior axis. The average error (difference between the marked point and the anatomical point) was 20.6%±5.9% (P=0.98) for the distal-proximal axis and 15.9%±6.1% (P=0.77) for the posterior-anterior axis.

Conclusions

The anatomical palpation technique showed low accuracy, even when performed by experienced surgeons. The most common error pattern observed was proximal and anterior.

Fluoroscopic guided tunnel placement during medial patellofemoral ligament reconstruction is not accurate in patients with severe trochlear dysplasia

PURPOSE

Accurate femoral tunnel placement is of great importance during medial patellofemoral ligament (MPFL) reconstruction. Purpose of the present study was to investigate the influence of trochlear dysplasia on the accuracy of fluoroscopic guided femoral tunnel placement.

METHODS

CT-Scans of 30 knees (five with regular shaped trochlea, 10 with a Type A and five each with a Type B, C, or D trochlear dysplasia) were imported into the image analysis platform MeVisLab. A 3D Bone Volume Rendering (VR) and a virtual lateral radiograph was created. The anatomic femoral MPFL insertion was identified on the 3D VR. On virtual lateral radiographs, the MPFL insertion was identified based on landmarks described by Schöttle et al. using three different perspectives: Best possible overlap of the femoral condyles (BC) and a tangent along posterior border of the posterior femoral cortex (pBC); a tangent along the anterior border of the posterior cortex (aBC); and best possible overlap of the distal part of the posterior femoral cortex (BF). Distances between the anatomic attachment and radiographically obtained insertions were measured on the 3D VR and compared according to the type of trochlear dysplasia.

RESULTS

Significantly lower accuracy of fluoroscopy guided tunnel placement in MPFL reconstruction was found in knees with Type C and D dysplasia. This effect was observed irrespectively from the radiologic perspective (pBC, aBC, and FC). In the pBC view (highest accuracy), the mean distance from the centre of the anatomic MPFL attachment to the radiographically defined location was 4.3 mm in knees without trochlear dysplasia and increased to 4.8 mm in knees with Type A dysplasia, 3.8 mm in knees with Type B dysplasia, 6.7 mm (p < 0.001) in knees with Type C dysplasia, and 7.3 mm (p < 0.001) in knees with Type D dysplasia.

CONCLUSION

Radiographic landmark-based femoral tunnel placement in the pBC view provides highest accuracy in knees with a normal shaped trochlea or low grade trochlear dysplasia. In patients with severe dysplasia, fluoroscopy guided tunnel placement has a low accuracy, exceeding a critical threshold of 5 mm distance to the anatomic MPFL insertion irrespective of the radiographic perspective. In these patients, utilization of anatomic landmarks may be beneficial.

LEVEL OF EVIDENCE

IV.

An Updated Overview of the Anatomy and Function of the Proximal Medial Patellar Restraints (Medial Patellofemoral Ligament and the Medial Quadriceps Tendon Femoral Ligament)

The medial patellofemoral ligament (MPFL) has been widely accepted to function as "the primary static restraint to lateral patellar displacement." However, current growing evidence suggests that there is a complex of medial patellofemoral/tibial ligaments, both proximal [MPFL, and medial quadriceps tendon femoral ligament (MQTFL)], and distal (medial patellotibial ligament and the medial patellomeniscal ligament) which restrain lateral patellar translation at different degrees of knee flexion. Specifically, the MQTFL has gained popularity over the last decade because of pure soft tissue attachments into the extensor mechanism that allow for avoidance of drilling tunnels into the patella during reconstruction. The purpose of this article was to report on the current knowledge (anatomy, biomechanics, diagnosis, indications for surgery, and techniques) on the proximal medial patellar restraints, namely the MPFL and the MQTFL, collectively referred to as the proximal medial patellar restraints.

Radiographic images are inapplicable for a precise evaluation of the femoral tunnel position following MPFL reconstruction

PURPOSE

In medial patellofemoral ligament (MPFL) reconstruction, it remains controversial whether more accurate femoral tunnel positioning is correlated with improved clinical outcomes. The purpose was to verify the accuracy of methods for evaluating tunnel positioning, one of which is the use of postoperative radiographs, in determining the femoral tunnel position following MPFL reconstruction and to compare the variability of tunnel positions to the intraoperatively documented positions on a true-lateral view.

METHODS

Seventy-three consecutive MPFL reconstructions were prospectively enrolled. Femoral tunnel positions were intraoperatively determined using fluoroscopy to obtain true-lateral radiographs. Postoperatively, lateral radiographic images were taken. Seven independent radiologists and seven independent orthopaedic knee surgeons evaluated the femoral tunnel position and amount of malrotation for each radiograph. Deviations from the Schoettle's point were measured and repeated after 4 weeks. Intraobserver and interobserver analyses of variance were calculated to determine the reliability of measurements on both intraoperative and postoperative radiographs.

RESULTS

Fifty-six patients were included in the final analysis. Tunnel positions were unable to be identified on postoperative radiographs in 14% of cases on average, independent of the degree of radiograph rotation. Intraoperative images showed mean deviations from the tunnel position to the centre of Schoettle's point of 1.9 ± 1.4 mm and 1.6 ± 1.0 mm in anterior-posterior and proximal-distal direction, respectively. Postoperative radiographs showed mean anterior-posterior and deviations of 7.4 ± 4.4 mm and 8.9 ± 5.8 mm assessed by orthopaedic surgeons and 10.6 ± 6.3 mm and 11.6 ± 7.1 mm assessed by radiologists at first and repeated measurement, respectively. The mean proximal-distal deviations were 4.8 ± 4.4 mm and 6.5 ± 6.0 mm and 7.2 ± 6.3 mm and 8.1 ± 7.1 mm, respectively. Measurement of tunnel position on intraoperative fluoroscopic images was significantly different compared to postoperative radiographs for each of the 14 observers (p < 0.05). Significant intraobserver and interobserver differences between the first and repeat measurements for both orthopaedic surgeons and radiologists were observed (p < 0.05).

CONCLUSION

Measurement of the femoral tunnel position on postoperative lateral radiographs is not an accurate or reliable method for evaluating tunnel position after MPFL reconstruction due to exposure, contrast, and malrotation of the radiograph from a true-lateral image. In contrast, intraoperative fluoroscopic control allows for a precise lateral view and correct tunnel positioning. Thus, postoperative radiographic images may be unnecessary for the evaluation of femoral tunnel positions, particularly when intraoperative fluoroscopy has been used.

STUDY DESIGN

Level II, prospective cohort study.

Recognition of evolving medial patellofemoral anatomy provides insight for reconstruction

PURPOSE

The scientific literature concerning the anatomy of medial soft-tissue stabilizers of the patella is growing exponentially. Much of the surgical literature has focused on the role of the medial patellofemoral ligament (MPFL) and techniques to reconstruct it, yet our understanding of its anatomy has evolved during the past several years. Given this, we report on the current understanding of medial patellofemoral anatomy and implications for reconstruction.

METHODS

Current and historical studies of medial patellar anatomy were reviewed, which include the MPFL and medial quadriceps tendon femoral ligament (MQTFL), as well as that of the distal medial patellar restraints, the medial patellotibial ligament (MPTL) and medial patellomeniscal ligament (MPML). In addition to the reported findings, the authors' anatomic descriptions of each ligament during their dissections were identified and recorded.

RESULTS

Despite the name of the MPFL, which implies that the ligament courses between the femur and patella, recent studies have highlighted the proximal MPFL fibers that attach to the quadriceps tendon, known as the MQTFL. The MPFL and MQTFL have also been referred to as the medial patellofemoral complex, reflecting the variability in anatomical attachment sites. The MPFL accounts for only half of the total restraint to lateral patellar displacement, and the remaining contributions to patellar stability are derived from the combination of the MPTL and MPML, which function primarily in greater degrees of knee flexion.

CONCLUSION

The understanding of the complexity of the medial patellar stabilizers continues to evolve. Although MPFL reconstruction is gaining wide acceptance as a procedure to treat patellar instability, it is important to recognize the complex and changing understanding of the anatomy of the medial soft-tissue stabilizers and the implications for reconstruction.

LEVEL OF EVIDENCE

V.

Comparation and evaluation of the accuracy of the sulcus localization method to establish the medial patellofemoral ligament femoral tunnel: a cadaveric and clinical study

Background

In anatomic medial patellofemoral ligament (MPFL) reconstruction, malpositioning of the MPFL femoral tunnel is common. A palpable sulcus reportedly exists at the anatomic femoral attachment of the MPFL. The present study aimed to investigate the accuracy of the sulcus localization method to establish the MPFL femoral tunnel.

Methods

A cadaveric study was first done on 12 knees to evaluate the accuracy of the sulcus localization method to establish the entry points of the MPFL femoral tunnel in comparison with the midpoint and fluoroscopic localization methods. The center of the native MPFL femoral attachment was served as the reference in the cadaveric study. A clinical study was then performed to further evaluate the accuracy of the sulcus localization method in 53 patients (60 knees). Schöttle’s point was served as the reference in the clinical study. Femoral tunnel placement was defined as accurate when it was less than 5 mm from Schöttle’s point. In both the cadaveric and clinical studies, MPFL femoral tunnel placement was assessed on postoperative reconstructed three-dimensional computed tomography images. In the cadaveric study, the accuracy of different localization methods was compared using analysis of variance.

Results

In the cadaveric study, the mean distances from the native MPFL attachment to the femoral tunnel entry point were 4.2 ± 1.0 mm (range 2.4–5.6 mm), 4.4 ± 1.4 mm (range 1.8–6.6 mm) and 2.9 ± 0.8 mm (range 1.9–4.4 mm) using the midpoint, fluoroscopic, and sulcus localization methods, respectively; this distance significantly differed between the midpoint and sulcus localization methods, and between the fluoroscopic and sulcus localization methods (p ≤ .05). While there were no significant differences between the midpoint and fluoroscopic localization methods (n.s.). In the clinical study, the mean distance between the femoral tunnel and Schöttle’s point was 3.5 ± 1.5 mm (range 0.4–6.1 mm), with accurate tunnel placement achieved in 49 of 60 cases (82%).

Conclusion

The sulcus localization method can accurately guide MPFL femoral tunnel placement. This method might be useful for orthopedic surgeons.

Level of evidence

IV

Intraoperative fluoroscopy during MPFL reconstruction improves the accuracy of the femoral tunnel position

PURPOSE

Reconstruction of the medial patellofemoral ligament (MPFL) has been established as standard of care for patellofemoral instability. An anatomic femoral tunnel position has been shown to be a prerequisite for restoration of patellofemoral stability and biomechanics. However, the incidence of malpositioning of the femoral tunnel during MPFL reconstruction continues to be notable. Palpation of anatomic landmarks and intraoperative fluoroscopy are the two primary techniques for tunnel placement. The aim of this study was to compare the accuracy of these two methods for femoral tunnel placement.

METHODS

From 2016 to 2017, 64 consecutive patients undergoing MPFL reconstruction for patelllofemoral instability were prospectively enrolled. During surgery, the presumed femoral MPFL insertion was identified by both palpation of anatomic landmarks and using fluoroscopy, both of these points were separately documented on true lateral radiographs. They were then analysed and deviations from the Schoettle's Point were measured as anterior-posterior and proximal-distal deviations. A tunnel position within a radius of 7 mm around the Schoettle's Point was designated as an "accurate tunnel position".

RESULTS

Compared to the method of palpation, fluoroscopy led to significantly more anatomic femoral tunnel positoning (p < 0.0001). The mean proximal-distal and anterior-posterior distances between the femoral insertion site identified by palpation and the Schoettle's Point were 5.7 ± 4.5 mm (0.3-20.3 mm) and 4.1 ± 3.7 mm (0.1-20.3 mm), respectively, versus 1.7 ± 0.9 mm (0.1-3.6 mm) and 1.8 ± 1.3 mm (0.1-4.8 mm) for fluoroscopy, respectively. Using fluoroscopy, all femoral insertion sites were identified within a 7 mm radius around the centre of the Schoettle's Point. In contrast, only 52% (33) of femoral insertion sites identified by palpation were within this radius. These data were independent of patients' age, gender and BMI. No improvement in accuracy of femoral tunnel positions was detected over time.

CONCLUSIONS

The main finding of this study was that, compared to the method of palpation of anatomic landmarks, the use of intraoperative fluoroscopy in MPFL reconstruction leads to more accurate femoral tunnel positioning. Based on these results, the use of intraoperative fluoroscopy has to be recommended for femoral tunnel placement in daily surgical practice to minimize the incidence of malpositioning and to restore native patellofemoral biomechanics.

STUDY DESIGN

Level III Case-control study.

The Relationship of Femoral Tunnel Positioning in Medial Patellofemoral Ligament Reconstruction on Clinical Outcome and Postoperative Complications

PURPOSE

To analyze the relation of the femoral tunnel (FT) positioning on clinical outcome.

METHODS

Patients with recurrent patellar dislocation who underwent medial patellofemoral ligament (MPFL) reconstruction with or without tibial tubercle osteotomy between 1998 and 2012 were included in this retrospective study. Strict postoperative lateral radiographs were mandatory. Knees with previous osseous stabilization surgery, fixed lateral patellar dislocation, valgus knee (>5°), or open growth plates were excluded. The distance between the FT and the validated radiographic landmark (the "Schoettle point") was measured. An FT with a distance greater than 10 mm was considered as malpositioned. The distance was correlated to subjective outcome measurements (patient satisfaction and Kujala score) and postoperative complications (a loss of range of motion and revision surgery).

RESULTS

Sixty-three knees in 60 patients (aged 23.7 ± 7.5 years at the time of surgery, 79.4% female) were included with a mean follow-up of 5.7 ± 3.3 years. The FT showed an average distance of 13.3 mm (±6.0 mm; 95% confidence interval [CI]: 11.7-14.8) to the Schoettle point, and 45 of 63 knees (71.4%) were deemed malpositioned. The postoperative Kujala score of malpositioned FT (75.9 points; 95% CI: 71.2-80.7) was not significantly inferior to knees with an FT within 10 mm (80.5; 95% CI: 73.7-87.3, P = .315). However, all 5 knees that underwent revision surgery showed an FT outside the 10-mm area.

CONCLUSIONS

Malpositioning of the FT in MPFL reconstruction is associated with postoperative complications. However, a malpositioned FT in MPFL reconstruction will not necessarily lead to an unsatisfactory subjective or objective clinical outcome. Other factors, such as surgical indication or graft tensioning, might also significantly influence postoperative outcome.

LEVEL OF EVIDENCE

Level IV, case-control study.

Lateral Patellar Instability in the Skeletally Mature Patient: Evaluation and Surgical Management

Lateral patellar instability is a common disease process that affects all types of patients. Depending on the patient's anatomy and the results of preoperative imaging, surgical management options include medial patellofemoral ligament reconstruction, tibial tubercle osteotomy, and sulcus-deepening trochleoplasty. Medial patellofemoral ligament reconstruction or repair is useful for almost all patients, whereas tibial tubercle osteotomy is helpful to correct a lateralized tibial tubercle and the associated elevated lateral pull of the extensor mechanism. For a select subset of patients with severe trochlear dysplasia, a sulcus-deepening trochleoplasty can be a useful option to prevent future patellar instability. Many technical considerations exist for each procedure, and in most situations, no consensus exists to direct surgeons on the superior technique.

Analysis of Graft Length Change Patterns in Medial Patellofemoral Ligament Reconstruction via a Fluoroscopic Guidance Method

BACKGROUND

A fluoroscopic guidance method for medial patellofemoral ligament (MPFL) reconstruction has been widely used to determine the anatomic femoral attachment site.

PURPOSE

To examine the graft length change patterns in MPFL reconstruction with a fluoroscopic guidance method.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Forty-four knees of 42 patients who underwent MPFL reconstruction for the treatment of recurrent patellar dislocation were examined prospectively. During surgery, suture anchors were inserted into the proximal one-third and center of the patella. A guide pin for the femoral tunnel was inserted into the position reported by Schöttle et al based on the true lateral view of the knee under fluoroscopic control. Changes in graft length patterns of the proximal and center anchors were examined through 0° to 120° of knee flexion. Favorable changes in length patterns were defined as meeting 2 of 3 criteria: (1) not long during flexion (≤3 mm between 30° and 120° of flexion) and either (2) nearly isometric during flexion between 0° and 90° or (3) slightly long during maximum extension (≤3 mm). Other patterns were considered unfavorable. If the change in length pattern was unfavorable, then the pin for the femoral tunnel was moved to different positions until it was favorable. Knees were separated into the favorable group and the unfavorable group. Differences between the groups regarding radiographic parameters were assessed. Student t test or chi-square test was used for statistical analysis.

RESULTS

Of the 44 knees, 31 (70.5%) showed favorable patterns. However, 13 knees (29.5%) showed unfavorable patterns; therefore, the position of the pin was changed. The mean ± SD distance from the original position to the final position was 5.3 ± 1.1 mm distal for 7 patients and 5.2 ± 0.4 mm posterodistal for 6 patients. Technical errors, including a nontrue lateral view and the tip of the wire not being in the determined area, were found for 4 of 13 knees in the unfavorable group. There was no statistical difference in radiographic parameters between the groups.

CONCLUSION

The graft length change pattern could be nonphysiologic at the position determined through the fluoroscopic guidance method; thus, caution may be necessary. The change in length pattern should be checked before graft fixation. If the length change pattern is unfavorable, then it is advisable to move it approximately 5 to 7 mm distally or posterodistally from the first position.

The trochlear isometric point is different in patients with recurrent patellar instability compared to controls: a radiographical study

PURPOSE

The purpose of the study was to investigate the theoretical isometric point based of the curve of the femoral groove and relating it to the origin of the MPFL femoral tunnel on lateral radiograph by comparing a patellar instability cohort with a control cohort.

METHODS

From a Patellar Instability database the radiographs of 40 consecutive patients were analysed to define Schöttle's point, and the arc of the circle of the trochlear groove. A comparison population of 20 radiographs from comparable patients with tibiofemoral joint disorders was used as a control. The distance from Schöttle's point to the most anterior part of the groove (extension) was also compared to the distance to the distal end of the roof of the notch (flexion).

RESULTS

The trochlea was circular in the controls but not the Patellofemoral Instability cohort where trochlear dysplasia is usually present. The difference between the extension and flexion length was a mean of - 2.0 ± 0.5 mm in the controls and + 6.0 ± 0.5 mm in the patellofemoral cohort. In neither cohort did the centre of the circle correspond to Schöttle's point. The extension distance correlated with the boss height.

CONCLUSIONS

The dysplastic trochlea is not circular and the centre of the best matched circle was different to the control trochleae which were circular. The circle centres did not correlate with Schöttle's point for either cohort, and was more proximal in the Patellofemoral Instability cohort.

CLINICAL RELEVANCE

For the MPFL to have equal tension throughout flexion within the groove, the length should not change. In normal knees the MPFL does not behave isometrically. The change in length, as measured from Schöttle's point to the trochlea, was greater for patellofemoral instability patients explaining why an isolated MPFL reconstruction in the presence of severe trochlear dysplasia risks poor outcomes. Level of evidence III.

Medial Patellofemoral Ligament Reconstruction Using Dual Patella Docking Technique

Medial patellofemoral ligament (MPFL) injuries are common in children and young adults. In patients with recurrent patellar dislocations with normal lower-extremity alignment, anatomic reconstruction of the MPFL has been shown to restore patellar stability. We describe a technique that creates an anatomic reconstruction using a dual docking technique into the patella. Our technique is simple and efficacious for reconstructing the MPFL without implant fixation in the patella, allowing a maximal bone-tendon interface for healing.

Impact of the patella height on the strain pattern of the medial patellofemoral ligament after reconstruction: a computer model-based study

PURPOSE

Medial patellofemoral ligament (MPFL) reconstruction is a key procedure for treating patellofemoral instability. However, controversy exists regarding the correct graft placement in different patellar heights. Therefore, our study aimed to investigate the influence of patellar height on MPFL insertion points.

METHODS

Strain patterns of the reconstructed MPFL were calculated using a dynamic musculoskeletal multibody simulation. Numerous patellar (proximal, central, distal) and femoral attachment sites (around the radiological point according to Schöttle) were analysed in the presence of different patella heights [Insall-Salvati (IS) indices 0.74, 1.0, 1.5] during dynamic knee flexion from 0° to 120°.

RESULTS

The reconstructed MPFL showed an almost isometric behaviour at the anatomic insertion (IS 1.0). Slight variation (<5 mm) around the ideal femoral insertion point resulted in only small changes in MPFL tension. However, a displacement of 10 mm led to a significant increase in MPFL tension, especially in the more anteriorly/proximally located femoral attachment points. Depending on the patella height, there exists an area of absolute isometry of the MPFL (length change <3 %) on the femoral condyle, which did not necessarily coincide exactly with the radiological point, but was located within a radius of 5 mm around it.

CONCLUSIONS

When reconstructed in the radiological femoral insertion point, MPFL strain patterns were only slightly affected by different patella heights (IS 0.74-1.5) suggesting that MPFL reconstruction could be safely performed using the radiological insertion. However, in case of a patella alta (IS 1.5), a slightly more proximal femoral insertion is beneficial for the biomechanical behaviour of the reconstructed MPFL.

Acquired femoral flexion deformity due to physeal injury during medial patellofemoral ligament reconstruction

BACKGROUND

Reconstruction of the medial patellofemoral ligament (MPFL) is the most frequent surgical procedure performed in patients with patellar instability. Recently, concerns regarding physeal injury during femoral tunnel placement for anatomical MPFL reconstruction in children have been discussed.

METHODS

This is the first case to report partial posterior physeal growth arrest and subsequent flexion deformity of the distal femur after MPFL reconstruction in a skeletally immature patient. The cause and treatment are discussed.

RESULTS

Postoperative knee extension deficit and recurrent patellar instability were successfully treated with revision surgery including, distal femoral extension osteotomy, medialization of the tibial tuberosity, trochleoplasty and MPFL graft tensioning.

CONCLUSION

This case highlights that care should be taken during femoral tunnel placement for anatomic graft fixation to avoid physeal injuries in skeletally immature patients.

Medial Patellofemoral Ligament Reconstruction Femoral Tunnel Accuracy: Relationship to Disease-Specific Quality of Life

Background:

Medial patellofemoral ligament (MPFL) reconstruction is a procedure aimed to reestablish the checkrein to lateral patellar translation in patients with symptomatic patellofemoral instability. Correct femoral tunnel position is thought to be crucial to successful MPFL reconstruction, but the accuracy of this statement in terms of patient outcomes has not been tested.

Purpose:

To assess the accuracy of femoral tunnel placement in an MPFL reconstruction cohort and to determine the correlation between tunnel accuracy and a validated disease-specific, patient-reported quality-of-life outcome measure.

Study Design:

Case series; Level of evidence, 4.

Methods:

Between June 2008 and February 2014, a total of 206 subjects underwent an MPFL reconstruction. Lateral radiographs were measured to determine the accuracy of the femoral tunnel by measuring the distance from the center of the femoral tunnel to the Schöttle point. Banff Patella Instability Instrument (BPII) scores were collected a mean 24 months postoperatively.

Results:

A total of 155 (79.5%) subjects had adequate postoperative lateral radiographs and complete BPII scores. The mean duration of follow-up (±SD) was 24.4 ± 8.2 months (range, 12-74 months). Measurement from the center of the femoral tunnel to the Schöttle point resulted in 143 (92.3%) tunnels being categorized as “good” or “ideal.” There were 8 failures in the cohort, none of which occurred in malpositioned tunnels. The mean distance from the center of the MPFL tunnel to the center of the Schöttle point was 5.9 ± 4.2 mm (range, 0.5-25.9 mm). The mean postoperative BPII score was 65.2 ± 22.5 (range, 9.2-100). Pearson r correlation demonstrated no statistically significant relationship between accuracy of femoral tunnel position and BPII score (r = –0.08; 95% CI, –0.24 to 0.08).

Conclusion:

There was no evidence of a correlation between the accuracy of MPFL reconstruction femoral tunnel in relation to the Schöttle point and disease-specific quality-of-life scores. Graft failure was not related to femoral tunnel placement. The patellofemoral instability population is complex, and patients present with multiple risk factors that, in addition to the accuracy of femoral tunnel position, contribute to quality of life and warrant further investigation.