The influence of medial patellofemoral ligament on patellofemoral joint kinematics and patellar stability

Effect of soft tissue tension around the knee joint on medio-lateral patellar position

Patellofemoral pain (PFP) is one of the most common sports injuries of the knee joint and has a high persistence and recurrence rate. Medio-lateral patellar position in the knee extension position during contraction is associated with PFP. However, soft tissue tension that most influences the medio-lateral patellar position in the knee extension position during contraction in vivo is unclear. We aimed to clarify the relationship between medio-lateral patellar position and soft tissue tension around the knee joint. Twelve patients with PFP and 20 healthy participants were included. Medio-lateral patellar position and tension of the rectus femoris, vastus lateralis (VL), vastus medialis, iliotibial band (ITB), lateral patellofemoral ligament, and medial patellofemoral ligament were measured during contraction and rest. The tensions of the VL and ITB during contraction and the medio-lateral patellar position at rest were significantly associated with medio-lateral patellar position during contraction (β = 0.449, 0.354, and 0.393, respectively). In addition, the tension of ITB was significantly associated with the medio-lateral patellar position at rest (β = 0.646). These relationships were not affected by the presence of PFP. These findings suggest that the patellar position during contraction became more lateral as the tension in the VL and ITB increased, regardless of the presence of PFP. These results may facilitate the prevention and treatment of PFP.

Reliability and validity of quantitative ultrasound for evaluating patellar alignment: A pilot study

BACKGROUND

Patellar malalignment is a risk factor of patellofemoral pain. Evaluation of the patellar alignment have mostly used magnetic resonance imaging (MRI). Ultrasound (US) is a non-invasive instrument that can quickly evaluate patellar alignment. However, the method for evaluating patellar alignment via US has not been established. This study aimed to investigate the reliability and validity of evaluating patellar alignment via US.

METHODS

The sixteen right knees were imaged via US and MRI. US images were obtained at two sites of the knee to measure US-tilt as the index of patellar tilt. Using a single US image, we measured US-lateral distance and US-angle as the index of patellar shift. All US images were obtained three times each by two observers to evaluate reliabilities. Lateral patellar angle (LPA), as the indicators of patellar tilt, and lateral patella distance (LPD) and bisect offset (BO), as the indicators of patellar shift, were measured via MRI.

RESULTS

US measurements provided high intra- (within-day and between days) and interobserver reliabilities with exception of interobserver reliability of US-lateral distance. Pearson correlation coefficient indicated that US-tilt is significantly positively correlated with LPA (r = 0.79), and US-angle is significantly positively correlated with LPD (r = 0.71) and BO (r = 0.63).

CONCLUSION

Evaluating patellar alignment via US showed high reliabilities. US-tilt and US-angle showed moderate to strong correlation with MRI indices of patellar tilt and shift via MRI, respectively. US methods are useful for evaluating accurate and objective indices of patellar alignment.

[Influence of the quadriceps muscles on the patellofemoral contact in patients with low flexion patellofemoral instability after MPFL reconstruction]

INTRODUCTION

MPFL reconstruction represents one of the most important surgical treatment options for recurrent patellar dislocations at low flexion angles associated with low flexion patellofemoral instability. Nevertheless, the role of quadriceps muscles in patients with patellofemoral instability before and after patellofemoral stabilization using MPFL reconstruction has not been fully elucidated. The present study investigates the influence of quadriceps muscles on the patellofemoral contact in patients with low flexion patellofemoral instability (PFI) before and after surgical patellofemoral stabilization using MPFL reconstruction using 3 T MRI datasets in early degrees of flexion (0-30°).

METHODS

In this prospective cohort study, 15 patients with low flexion PFI before and after MPFL reconstruction and 15 subjects with healthy knee joints were studied using dynamic MRI scans. MRI scans were performed in a custom-made pneumatic knee loading device to determine the patellofemoral cartilage contact area (CCA) with and without quadriceps activation (50 N). Comparative measurements were performed using 3D cartilage and bone meshes in 0-30° knee flexion in the patients with patellofemoral instability preoperatively and postoperatively.

RESULTS

The preoperative patellofemoral CCA of patients with low flexion PFI was 67.3 ± 47.3 mm2 in 0° flexion, 118.9 ± 56.6 mm2 in 15° flexion, and 267.6 ± 96.1 mm2 in 30° flexion. With activated quadriceps muscles (50 N), the contact area was 72.4 ± 45.9 mm2 in extension, 112.5 ± 54.9 mm2 in 15° flexion, and 286.1 ± 92.7 mm2 in 30° flexion without statistical significance. Postoperatively determined CCA revealed 159.3 ± 51.4 mm2 , 189.6 ± 62.2 mm2 and 347.3 ± 52.1 mm2 in 0°, 15° and 30° flexion. Quadriceps activation with 50 N showed a contact area in extension of 141.0 ± 63.8 mm2, 206.6 ± 67.7 mm2 in 15° flexion, and 353.5 ± 64.6 mm2 in 30° flexion, also without statistical difference compared with unloaded CCAs. Subjects with healthy knee joints showed an increase of 10.3% in CCA at 30° of flexion (p = 0.003).

CONCLUSION

Although patellofemoral CCA increases significantly after isolated MPFL reconstruction in patients with low flexion patellofemoral instability, there is no significant influence of quadriceps muscles either preoperatively or postoperatively.

Outcomes After Derotational Distal Femoral Osteotomy for Recurrent Patellar Dislocations With Increased Femoral Anteversion: A Systematic Review and Meta-analysis

Background

An increased femoral anteversion angle (FAA) is a predisposing factor for recurrent patellar dislocations (RPDs), and combined procedures including derotational distal femoral osteotomy (DDFO) have been shown to be good options.

Purpose

To investigate the safety and effectiveness of combined DDFO on clinical and radiological outcomes to treat RPDs with an increased FAA.

Study Design

Systematic review; Level of evidence, 4.

Methods

This review was performed according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) guidelines. We searched 7 databases for articles from inception to March 10, 2023, that reported outcomes after combined DDFO in patients with an RPD and increased FAA. Two reviewers independently extracted data and assessed study quality. Outcomes evaluated were functional scores, redislocation rates, complications, satisfaction, and radiological parameters. A meta-analysis was performed to pool functional scores, with data reported as mean differences (MDs) and 95% confidence intervals (CIs).

Results

Included were 8 studies of 189 knees from 183 patients, with a mean patient age of 22.4 years and a mean follow-up of 33.4 months. The mean preoperative FAA ranged from 31° to 42.70°, and the mean postoperative FAA ranged from 10° to 19.08°. Significant improvements were found in the Kujala score (MD, 26.96 [95% CI, 23.54 to 30.37]), Lysholm score (MD, 26.17 [95% CI, 22.13 to 30.22]), visual analog scale score for pain (MD, -2.61 [95% CI, -3.12 to -2.10]), and Tegner activity score (MD, 1.33 [95% CI, 0.86 to 1.79]). No subluxation or redislocation occurred. The overall complication rate was 10.6%, and most of the complications were pain (60%) and limited knee activity (20%). The overall satisfaction rate was 83.3%. The patellar tilt angle significantly decreased from 40.7° ± 11.9° to 20.5° ± 8.7° and from 26.35° ± 6.86° to 11.65° ± 2.85° in 2 studies.

Conclusion

Combined DDFO was found to be safe and effective for the treatment of RPDs and an increased FAA by addressing both patellar dislocations and torsional malalignment. However, because of the lack of comparisons, it remains to be investigated when DDFO should be combined in such patients.

Influence of Medial Patellofemoral Ligament Reconstruction on Patellofemoral Contact in Patients With Low-Flexion Patellar Instability: An MRI Study

Background

Medial patellofemoral ligament (MPFL) reconstruction is a well-established procedure for the treatment of patients with patellofemoral instability (PFI) at low flexion angles (0°-30°). Little is known about the effect of MPFL surgery on patellofemoral cartilage contact area (CCA) during the first 30° of knee flexion.

Purpose/Hypothesis

The purpose of this study was to investigate the effect of MPFL reconstruction on CCA using magnetic resonance imaging (MRI). We hypothesized that patients with PFI would have a lower CCA than patients with healthy knees and that CCA would increase after MPFL reconstruction over the course of low knee flexion.

Study Design

Cohort study; Level of evidence, 2.

Methods

In a prospective matched-paired cohort study, the CCA of 13 patients with low-flexion PFI was determined before and after MPFL reconstruction, and the data were compared with those of 13 healthy volunteers (controls). MRI was performed with the knee at 0°, 15°, and 30° of flexion in a custom-designed knee-positioning device. To suppress motion artifacts, motion correction was performed using a Moiré Phase Tracking system via a tracking marker attached to the patella. The CCA was calculated on the basis of semiautomatic cartilage and bone segmentation and registration.

Results

The CCA (mean ± SD) at 0°, 15°, and 30° of flexion for the control participants was 1.38 ± 0.62, 1.91 ± 0.98, and 3.68 ± 0.92 cm², respectively. In patients with PFI, the CCA at 0°, 15°, and 30° of flexion was 0.77 ± 0.49, 1.26 ± 0.60, and 2.89 ± 0.89 cm² preoperatively and 1.65 ± 0.55, 1.97 ± 0.68, and 3.52 ± 0.57 cm² postoperatively. Patients with PFI exhibited a significantly reduced preoperative CCA at all 3 flexion angles when compared with controls (P ≤ .045 for all). Postoperatively, there was a significant increase in CCA at 0° of flexion (P = .001), 15° of flexion (P = .019) and 30° of flexion (P = .026). There were no significant postoperative differences in CCA between patients with PFI and controls at any flexion angle.

Conclusion

Patients with low-flexion patellar instability showed a significant reduction in patellofemoral CCA at 0°, 15°, and 30° of flexion. MPFL reconstruction increased the contact area significantly at all angles.

Reconstruction of the medial patellofemoral ligament with nonresorbable suture tape normalizes patellar maltracking independent of patella-side fixation technique

PURPOSE

Patellar maltracking caused by a rupture of the medial patellofemoral ligament (MPFL) can be improved by MPFL reconstruction (MPFL-R) with a tendon graft. Nonresorbable suture tape (FiberTape^®, FT) is possibly becoming an option to tendon grafts for MPFL-R. Patella-side fixation of FT can be performed with suture anchors or via soft-tissue fixation. The aim of this study was to investigate patellar tracking considering soft-tissue-based and anchor-based patella-side fixation techniques.

METHODS

In eight fresh-frozen human knee joint specimens (m/f 4/4; age 75 ± 10 years), the MPFL was identified, and a rupture was placed near the femoral insertion site. In the study group (SG; 4 knees), soft-tissue fixation of the FT was performed at the medial patellar retinaculum; in the control group (CG; 4 knees), FT was fixed at the patella via suture anchors. For native MPFL (nMPFL), ruptured ("injured") MPFL (iMPFL) and reconstructed MPFL (FT-MPFL-SG, respectively, FT-MPFL-CG) cone beam CT scans were performed in 15°, 30°, and 45° of knee joint flexion. Patellar tracking was assessed using the radiological parameters patellar tilt (PT), congruence angle (CA) and posterior patellar edge-trochlear groove ratio (PTR).

RESULTS

All recorded radiological parameters increased, respectively, decreased in the CG and SG from the nMPFL to the iMPFL state. After MPFL-R, all parameters normalized when compared to the intact state (nMPFL), regardless of patella-side fixation technique. All investigated parameters of patellotrochlear alignment were positively, respectively, negatively significantly (p < 0.05) correlated throughout all evaluated conditions (nMPFL, iMPFL, FT-MPFL-SG, FT-MPFL-CG).

CONCLUSION

MPFL-R with a nonresorbable suture tape can normalize patellar maltracking in fresh-frozen human knee joint specimens in earlier degrees of knee joint flexion independent of patella-side fixation technique. The investigated parameters of patellotrochlear alignment correlate with each other.

Groove-deepening trochleoplasty reduces lateral patellar maltracking and increases patellofemoral contact pressures: Dynamic simulation

Groove-deepening trochleoplasty is performed to restore patellar stability by increasing the lateral constraint applied to the patella by the trochlear groove. Multibody dynamic simulation of knee function was used to characterize the influence of groove-deepening trochleoplasty on patellar tracking and patellofemoral contact pressures. Computational models were created to represent seven knees with trochlear dysplasia, indicated by a flat trochlear groove and supratrochlear spur. The models were manipulated to remove the spur and deepen the trochlear groove to represent the average shape following a trochleoplasty. Knee squatting was simulated for the preoperative and postoperative conditions. Statistically significant (p < 0.05) differences in output parameters were identified with repeated measures comparisons at every 5° of knee flexion. Trochleoplasty significantly decreased lateral patellar tracking, particularly at low knee flexion angles. Trochleoplasty decreased the peak lateral shift of the patella (bisect offset index) with the knee extended from 0.87 ± 0.14 to 0.75 ± 0.12. Trochleoplasty also significantly decreased the contact area and increased the maximum contact pressure at multiple flexion angles. Trochleoplasty decreased the average contact area by approximately 10% in mid-flexion, with a corresponding increase in the average maximum contact pressure of 13%-23%. Decreased contact area and increased contact pressures are related to altered patellofemoral congruity due to reshaping the femur without a corresponding change to the patella. Clinical significance: The results indicate groove-deepening trochleoplasty decreases lateral patellar maltracking, reducing the risk of patellar dislocations, but can elevate patellofemoral contact pressures, which could contribute to long-term degradation of cartilage.

[Three-dimensional finite element study on combined proximal and distal knee extension rearrangement for recurrent patellar dislocation]

OBJECTIVE

To establish a three-dimensional finite element analysis model of the knee joint in fresh frozen cadavers, to verify the validity of the model and to simulate the stress distribution characteristics of the patellofemoral joint after combined proximal and distal knee extension rearrangement surgery for recurrent patellar dislocation.

METHODS

One male and one female fresh frozen cadavers (4 knees in total), using voluntary body donations, were used to measure the maximum pressure on the patellofemoral articular surface at each passive flexion angle (0°, 30°, 60°, 90°, 120°) of the normal knee joint and the model after combined proximal and distal knee extension rearrangement surgery for recurrent patellar dislocation with tibial tuberosity-trochlear groove distance (TT-TG) value >2.00 cm using pressure-sensitive paper, respectively. Then, the 2 freshly frozen cadavers were used to construct three-dimensional finite element models of normal knee joints and postoperative knee joints, and the maximum pressure on the patellofemoral articular surface was measured at various passive flexion angles. The maximum pressure was compared with the measurement results of the pressure-sensitive paper to verify the validity of the three-dimensional finite element model. In addition, the maximum pressure on the patellofemoral joint surface measured by three-dimensional finite element was compared between the normal knee joint and the postoperative knee joint at various passive flexion angles, so as to obtain an effective three-dimensional finite element model for the simulation study of the stress distribution characteristics of the patellofemoral joint after combined proximal and distal knee extension rearrangement surgery for recurrent patellar dislocation.

RESULTS

The maximum pressure on the patellofemoral joint surface measured by pressure-sensitive paper and three-dimensional finite element measurements were similar at all passive flexion angles in the normal knee joint, with a difference of -0.08-0.06 MPa; the maximum pressure on the patellofemoral joint surface measured by pressure-sensitive paper and three-dimensional finite element measurements were also similar at all passive flexion angles in the knee after combined proximal and distal knee extension rearrangement surgery, with a difference of -0.04-0.09 MPa. The maximum pressure on the patellofemoral joint surface measured by three-dimensional finite elements were also similar between the normal knee joint and the knee joint after combined proximal and distal knee extension rearrangement surgery at all passive flexion angles, with a difference of -0.50--0.03 MPa.

CONCLUSION

The three-dimensional finite element model of the normal knee joint and the knee joint after combined proximal and distal knee extension rearrangement surgery can accurately and effectively quantify the change in the maximum pressure on the patellofemoral joint surface; for recurrent patellar dislocations with TT-TG value>2.00 cm, the combined proximal and distal knee extension rearrangement surgery can achieve a maximum pressure of the patellofemoral joint surface similar to that of the normal knee joint.

Medial patellofemoral ligament reconstruction with autologous gracilis tendon: Clinical and radiological outcomes at a mean 6 years of follow up

BACKGROUND

The medial patellofemoral ligament (MPFL) is considered the primary soft tissue restrain to lateral translation of the patella during the first 15-30 degrees of knee flexion. The primary restraint thereafter is the slope of the lateral wall of the trochlea. A plenty of procedures are described in literature for MPFL reconstruction with different types of graft, angle of knee flexion for fixation and rehabilitation protocols. In this study we used MPFL reconstruction with doubled autologous gracilis tendon with the Schottle's technique. The aim of our study is to evaluate outcomes at medium-long term follow up of MPFL reconstruction.

METHODS

Patients who underwent arthroscopic MPFL reconstruction for recurrent patellar dislocation were followed up for a minimum of 2 to 10 years. Patient-reported outcomes including the Kujala, Visual Analogue Scale (VAS) score were collected preoperatively and postoperatively. Clinical complications such as loss of ROM, recurrent sub-luxation or dislocation were recorded.

RESULTS

A total of 38 patients with recurrent patellar dislocation were treated with MPFL reconstruction and data were available for final follow up (mean 72.3 months, SD 33.6). Mean age at time of surgery was 23.4 (SD 7.8). Mean number of dislocations before surgery was 7.1 (SD 10.5). Recurrent dislocations were not observed in any of the patients treated at last follow-up. Significant clinical improvements were also noted with Kujala and VAS score. Patellar tilt angle decreased significantly from pre to post-operative.

CONCLUSION

Our study demonstrated that MPFL reconstruction with patellar suture anchors fixation using autologous gracilis tendon is an effective, safe and reliable method for treating recurrent patellar dislocation.

Comparing Nonoperative Treatment, MPFL Repair, and MPFL Reconstruction for Patients With Patellar Dislocation: A Systematic Review and Network Meta-analysis

Background:

Medial patellofemoral ligament (MPFL) reconstruction, MPFL repair, and nonoperative treatment are important treatments for patients with patellar dislocation. However, it is unclear which treatment leads to better outcomes.

Purpose:

To determine the efficacy and safety of the 3 treatments in the treatment of patellar dislocation and compare the effect of MPFL reconstruction with MPFL repair, MPFL reconstruction with nonoperative treatment, and MPFL repair with nonoperative treatment.

Study Design:

Systematic review; Level of evidence, 3.

Methods:

The PubMed, Web of Science, Cochrane Library, Embase, CNKI (China National Knowledge Infrastructure), and Wanfang databases were searched from inception to December 2020. Included were clinical studies that described the efficacy and safety of 2 of the 3 treatments, studies directly comparing the clinical effects of the 2 operative techniques, or studies comparing the effects of reconstruction or repair with nonoperative treatment. Two reviewers independently extracted data and assessed the quality of the included studies with the Cochrane risk-of-bias tools. The outcomes evaluated were postoperative redislocation rate, revision rate, complications, and Kujala score. We used traditional direct pairwise meta-analysis as well as network meta-analysis for comprehensive efficacy of all 3 treatment measures.

Results:

Twelve studies were included: 5 compared MPFL reconstruction with MPFL repair, 2 compared MPFL reconstruction with nonoperative treatment, and 5 compared MPFL repair with nonoperative treatment. The risk of bias was serious in 4, moderate in 4 and low in 4 articles. MPFL reconstruction led to significantly reduced redislocation and improved Kujala scores compared with MPFL repair and nonoperative treatment. MPFL repair led to reduced redislocation rates compared with nonoperative treatment but did not show an obvious benefit in primary dislocations. There was no significant difference among the 3 treatments in terms of revision rate and incidence of complications, although we found that treatment-related complications were least likely to occur in nonoperative treatment.

Conclusion:

The results of this review indicate that MPFL reconstruction decreases recurrent dislocation compared with MPFL repair or nonoperative treatment, but it has a higher possibility of complications. MPFL repair resulted in less postoperative redislocation than nonoperative treatment but did not show an obvious benefit in primary dislocation.

Studies of the criteria for determining optimal location of medial patellofemoral ligament attachment sites

Identifying appropriate attachment sites is important in the planning of medial patellofemoral ligament (MPFL) reconstruction. Two criteria are advanced to describe normal MPFL function, namely isometric criterion and desired pattern criterion. Subsequently, computational methods have applied these criteria to determine optimal attachment sites. So far, there is no study that compares the outcomes of these two criteria. For five subjects' 3D models of the patella and femur, three patellar sites and many femoral sites were identified as pairs of candidate attachment sites. For each patellar site, the criteria were applied to identify the matching femoral sites that satisfy them. The matching femoral site with the smallest length change was identified as the optimal femoral site. The desired pattern criterion finds fewer matching sites compared to the isometric criterion. In contrast, the isometric criterion can always find matching sites. The optimal femoral sites obtained vary significantly across different subjects. For most subjects, the optimal sites obtained using the isometric criterion are closer to known anatomical sites than those obtained using the desired pattern criterion. This study reaffirms that MPFL reconstruction is subject specific. The isometric criterion may be more reliable than the desired pattern criterion for determining optimal attachment sites. Graphical Abstract. Highlight of the paper. The location of the patella site significantly affects the location of the optimal femoral site. The isometric criterion option 1, with length at 0° regarded as MPFL's natural length, may be more reliable than other criteria or options for the planning of MPFL surgery because the optimal sites that it finds are closest to known anatomical sites.ᅟ.

Medial Patellotibial Ligament Reconstruction Improves Patella Tracking When Combined With Medial Patellofemoral Reconstruction: An In Vitro Kinematic Study

PURPOSE

To investigate the isolated and combined effects of medial patellofemoral ligament (MPFL) and medial patellotibial ligament (MPTL) deficiency and reconstruction on patellofemoral kinematics.

METHODS

Sixteen matched-paired female cadaveric knee specimens with a mean age of 53.5 years (range, 26-65) were tested in 5 conditions: (1) intact, (2) MPFL or MPTL cut, (3) MPFL and MPTL combined cut, (4) MPFL or MPTL reconstruction, and (5) MPFL and MPTL combined reconstruction. Dynamic testing allowed continuous analysis of kinematics from 0° to 90° of knee flexion. Knees were also tested statically using a lateral load of 45 N at 0°, 30°, 60°, and 90° of flexion. In both dynamic and static loading tests, a motion capture system detected patellar position for each testing state to distinguish changes in patellar kinematics. Random-intercepts linear mixed-effects models were used to compare patellar kinematics.

RESULTS

The MPFL is the primary restraint to lateral translation of the patella at all knee flexion angles. MPTL deficiency alone did not create significant patella instability, but further increased instability when the MPFL was deficient. Isolated MPFL and combined reconstruction provided improved stability. Through full range of motion native patella tracking was best recreated with combined ligament reconstruction.

CONCLUSIONS

The MPFL plays the greatest role in medial patellar stability, but the MPTL appears to have an influence on patella tracking. This study provides further understanding to the impact of the MPFL and MPTL on patellofemoral motion with implications for reconstruction to improve stability and optimize patellofemoral tracking.

CLINICAL RELEVANCE

This study provides further understanding of the role of the MPFL and MPTL on patellofemoral motion with implications for reconstruction to improve stability and optimize patellofemoral tracking.

Recurrent Patellar Dislocations Without Untreated Predisposing Factors: Medial Patellofemoral Ligament Reconstruction Versus Other Medial Soft-Tissue Surgical Techniques-A Meta-analysis

PURPOSE

To provide a direct comparison between medial patellofemoral ligament (MPFL) reconstruction and the other medial patellofemoral soft-tissue surgeries in the restoration of the medial patellar restraint after lateral patellar dislocations in the absence of untreated predisposing factors such as high grade trochlear dysplasia, knee malalignment, patella alta or high tibial tubercle-trochlear groove distance.

METHODS

PubMed, Cochrane-library, Web of Science, and gray literature databases were searched to find all the relevant records. Study selection, data extraction, and risk of bias assessment were performed following the Cochrane and Preferred Reporting Items for Systematic Reviews and Meta-analysis guidelines. Different techniques to treat lateral patellar dislocation in the absence of untreated predisposing factors were compared in terms of redislocation and complication rates, Kujala, Lysholm, International Knee Documentation Committee, and Tegner scores at the short-term (3 years) and long-term (>3 years) follow-up through meta-analyses.

RESULTS

Six studies involving 319 knees were included in the meta-analysis. The analyses of redislocation (0.7% vs 2.9%) and minor complication rates (12% vs 9%) showed no significant differences between MPFL reconstruction and other medial soft-tissue surgeries. Significant differences favoring MPFL reconstruction were documented in Kujala and Lysholm scores at short-term (8.6, P< .001; 10.9, P < .001) and long-term follow-ups (6.3, P = .02; 13.5, P < .001). No significant differences were found in the analyses of International Knee Documentation Committee (P = .10) and Tegner scores (P = .19). Level of evidence was low or very low.

CONCLUSIONS

MPFL reconstruction and medial patellofemoral soft-tissue surgery procedures were both effective in restoring the medial restraining forces preventing redislocation, but MPFL reconstruction provided better functional outcomes both at short-term and long-term follow-up. Thus, besides the treatment of predisposing factors, MPFL reconstruction seems to be, based on the results of this meta-analysis, a suitable strategy to restore the medial restraining function in the treatment of recurrent LPD.

LEVEL OF EVIDENCE

Level III (meta-analysis of randomized and nonrandomized comparative trials).

Patellofemoral Contact Pressure for Medial Patellofemoral Ligament Reconstruction Using Suture Tape Varies With the Knee Flexion Angle: A Biomechanical Evaluation

PURPOSE

The purpose of this study was to evaluate the effect of the knee flexion angle during graft fixation on patellofemoral (PF) contact pressure in medial patellofemoral ligament (MPFL) reconstruction using polyester suture tape and knotless anchors.

METHODS

Nine human knees (mean age 74.9 ± 14.1 years) were used in this study. Polyester suture tape was fixed at the medial edge of the patella with two 3.5-mm knotless anchors, and then to the femur with a 4.75-mm knotless anchor at 4 different knee flexion angles (0°, 30°, 60°, and 90°). A pressure sensor was used to measure the maximum contact pressure (MCP) of the medial and lateral PF joints in the intact knee and in postreconstruction knees at each knee flexion angle (0°, 30°, 60°, and 90°). Each MCP was normalized to that of the intact knee. A statistical comparison was made between MCP in the intact and reconstructed knees.

RESULTS

The normalized MCP of the medial PF joint fixed at either 0° or 30° significantly increased at 60° of knee flexion (P = .036 and .042, respectively) and at 90° of knee flexion (P = .002 and .001, respectively). Conversely, the normalized MCP fixed at 60° and 90° remained at the same level as the intact knees at all angles of knee flexion. The normalized MCP of the lateral PF joint showed no significant difference at any fixation angle compared with intact knees.

CONCLUSION

To avoid excessive PF joint contact pressure after MPFL reconstruction, it may be best to fix polyester suture tape between 60° and 90° of knee flexion.

CLINICAL RELEVANCE

Fixation of the polyester suture tape with a knotless anchor for MPFL reconstruction should be at 60° to 90° of knee flexion to most closely restore PF joint contact pressures to that of the intact knee.

How tibial tubercle torsion impacts patellar stability: A biomechanics study

INTRODUCTION

A new factor for patellofemoral instability-external torsion of the tibial tubercle-has recently been described. The primary aim of this biomechanics study was to analyze the consequences of internal torsion tibial tubercle osteotomy (TTO) on an experimentally unstable patella. We hypothesized that internal TTO can stabilize an experimental patellar instability.

MATERIALS AND METHODS

This in vitro study was conducted on six fresh anatomical specimens. The knees were flexed to 25°. The patella was destabilized by transecting the patellar retinaculae and the vastus medialis tendon and by applying continuous oblique traction on the quadriceps tendon. A 3D stereovision system was used to record patellar displacement and tilt and to determine whether patellar dislocation occurred. The measurements were done before the osteotomy then repeated on the same knee after a triangular internal torsion 30° TTO was completed, without medialization.

RESULTS

There was a significant difference in the patellar displacement and tilt before and after the osteotomy (p<0.05). Patellar dislocation, which was induced by traction on all the knees before osteotomy, did not occur after the osteotomy was performed.

DISCUSSION

Internal torsion of the tibial tubercle improves patellar stability, confirming our hypothesis. These findings confirm the stabilizing effect of placing the tibial tuberosity in internal torsion. Although a knee without instability factors is not the perfect model for patellar instability, our findings suggest that tibial tubercle torsion influences patellar stability. Internal TTO may be justified as a surgical treatment of patellofemoral instability.

Neither lateral patellar facet nor patellar size are altered in patellofemoral unstable patients: a comparative magnetic resonance imaging analysis

PURPOSE

It remains unclear if morphologic patterns of the patella itself predispose to patellar instability. This study examined established patellar landmarks in relation to the femoral condyle width to clarify differences of patellar morphologies in patellofemoral stable and unstable patients.

METHODS

Magnetic Resonance Imaging of 50 subjects (20.7 ± 4.4 years; 17 males, 33 females) with patellofemoral instability (study group, SG) and 50 subjects (25.3 ± 5.8 years; 31 males, 19 females) with anterior cruciate ligament rupture (control group, CG) were analyzed. Corresponding patellar value indices (PW-I; LPF-I 1; LPF-I 2) in relation to the femoral condyle width (FCW) were evaluated after the measurement of absolute patellar dimension [patellar width (PW); direct length of the lateral patellar facet (LPF-1); projected length of the lateral patellar facet (LPF-2)]. The patellar shape according to Wiberg, trochlear dysplasia, patellar height, and tibial tubercle-trochlear groove (TT-TG) distance were determined.

RESULTS

The SG showed a significantly longer absolute (LPF 2) (P = 0.041) and relative (LPF-I 1, LPF-I 2) (P < 0.001) lateral facet of the patella. No significant differences were evaluable for the relative patellar width (PW-I) (ns). A patellar shape type 3 (P = 0.001) as well as a higher position of the patella and TT-TG-distance (P < 0.001) were significantly more often present in the SG.

CONCLUSION

There are several bony alterations associated with patellofemoral instability, but our data did not show a significantly smaller lateral patellar facet or relative patellar width that could facilitate a patellar dislocation. This helps surgeons, that are considering to surgically address the patella in cases of patellofemoral instability, to better understand its morphologic pattern.

LEVEL OF EVIDENCE

III.

Selective bundle tensioning in double-bundle MPFL reconstruction to improve restoration of dynamic patellofemoral contact pressure

PURPOSE

To evaluate the optimal graft tension angles in a medial patellofemoral ligament (MPFL) reconstruction with selective bundle tensioning in order to restore patellofemoral contact pressure distributions closest to the native state.

METHODS

Twelve human cadaveric knee specimens were mounted with the femur on a custom-made fixation device allowing free range of motion in the knee joint for testing. Using a sensitive pressure film (Tekscan) patellofemoral contact pressure was measured in 15° intervals during a dynamic flexion movement from 0°-90° in the native state, in cut MPFL and after MPFL-reconstruction with a gracilis tendon. The graft was separated in two bundles and was fixed independently on the patella using two knotless anchors. Two groups were made with either the proximal or distal bundle fixed at the femur at a knee flexion angle of 30° and the corresponding other bundle subsequently fixed at the femur at 15°, 45°, 60°, 75° and 90° of knee flexion using extra-cortical fixation and controlled tension of 2N in both groups. The sequence of the flexion angles at the graft fixation was alternated. Pressure measurements were repeated after every fixation of the graft.

RESULTS

Cutting the MPFL resulted in significantly reduced patellofemoral contact pressure at all flexion angles. After MPFL reconstruction the patellofemoral contact pressure remained significantly reduced during dynamic knee flexion in all tested double-bundle combinations (p < 0.05) except for fixation of the proximal bundle in 30° and the distal bundle in 75°. Selective evaluation of lateral patellofemoral contact pressure, however, showed significant reduction in all tested double-bundle combinations (p < 0.05) from 15° to 90°. Evaluation of isolated medial patellofemoral pressure changes showed no significant difference in all tested combinations compared to the intact knee. Furthermore, evaluation of the isolated proximal and distal patellofemoral contact pressure also revealed a significantly reduced contact pressure in all tested double-bundle combinations (p < 0.05) except for fixation of the proximal bundle in 30° and the distal bundle in 75°.

CONCLUSION

According to this study, selective bundle tensioning in anatomic MPFL-reconstruction should be considered as an easy and more anatomic alternative to current popular techniques to restore patella kinematics and give clear recommendation about knee flexion angle and tension during fixation. Although tensioning two bundles separately may further improve clinical results. If performed, fixation of the graft is recommended under low tension (2N) with the proximal bundle at 30° and the distal bundle at 75° of knee flexion.

Properties and Function of the Medial Patellofemoral Ligament: A Systematic Review

BACKGROUND

As the main passive structure preventing patellar lateral subluxation, accurate knowledge of the anatomy, material properties, and functional behavior of the medial patellofemoral ligament (MPFL) is critical for improving its reconstruction.

PURPOSE

To provide a state-of-the-art understanding of the properties and function of the MPFL by undertaking a systematic review and statistical analysis of the literature.

STUDY DESIGN

Systematic review.

METHODS

On June 26, 2018, data for this systematic review were obtained by searching PubMed and Scopus. Articles containing numerical information regarding the anatomy, mechanical properties, and/or functional behavior of the MPFL that met the inclusion criteria were reviewed, recorded, and statistically evaluated.

RESULTS

A total of 55 articles met the inclusion criteria for this review. The MPFL presented as a fanlike structure spanning from the medial femoral epicondyle to the medial border of the patella. The reported data indicated ultimate failure loads from 72 N to 208 N, ultimate failure elongation from 8.4 mm to 26 mm, and stiffness values from 8.0 N/mm to 42.5 N/mm. In both cadaveric and in vivo studies, the average elongation pattern demonstrated close to isometric behavior of the ligament in the first 50° to 60° of knee flexion, followed by progressive shortening into deep flexion. Kinematic data suggested clear lateralization of the patella in the MPFL-deficient knee during early knee flexion under simulated muscle forces.

CONCLUSION

A lack of knowledge regarding the morphology and attachment sites of the MPFL remains. The reported mechanical properties also lack consistency, thus requiring further investigations. However, the results regarding patellar tracking confirm that the lack of an MPFL leads to lateralization of the patella, followed by delayed engagement of the trochlear groove, plausibly leading to an increased risk of patellar dislocations. The observed isometric behavior up to 60° of knee flexion plausibly suggests that reconstruction of the ligament can occur at flexion angles below 60°, including the 30° and 60° range as recommended in previous studies.

Repair of the medial patellofemoral ligament with suture tape augmentation leads to similar primary contact pressures and joint kinematics like reconstruction with a tendon graft: a biomechanical comparison

PURPOSE

To compare suture tape-augmented MPFL repair with allograft MPFL reconstruction using patellofemoral contact pressure and joint kinematics to assess the risk of patellofemoral over-constrainment at point zero.

METHODS

A total of ten fresh frozen cadaveric knee specimens were tested in four different conditions of the MPFL: (1) native, (2) cut, (3) reconstructed with tendon graft, and (4) augmented with suture tape. The patellofemoral mean pressure (MP), peak pressure (PP) and contact area (CA) were measured independently for the medial and lateral compartments using pressure-sensitive films. Patellar tilt (PT) and shift (PS) were measured using an optical 3D motion tracking system. Measurements were recorded at 0°, 10°, 20°, 30°, 60° and 90° of flexion. Both the tendon graft and the internal brace were preloaded with 2 N, 5 N, and 10 N.

RESULTS

There was no significant differences found between surgical methods for medial MP, medial PP, medial CA, lateral MP and PS at any preload or flexion angle. Significant differences were seen for lateral PP at 20° knee flexion and 10 N preload (suture tape vs. reconstruction: 1045.9 ± 168.7 kPa vs. 1003.0 ± 151.9 kPa; p = 0.016), for lateral CA at 10° knee flexion and 10 N preload (101.4 ± 39.5 mm² vs. 108.7 ± 36.6 mm²; p = 0.040), for PT at 10° knee flexion and 2 N preload (- 1.9 ± 2.5° vs. - 2.5 ± 2.3°; p = 0.033) and for PT at 0° knee flexion and 10 N preload (- 0.8 ± 2.5° vs. - 1.8 ± 3.1°; p = 0.040). A preload of 2 N on the suture tape was the closest in restoring the native joint kinematics.

CONCLUSIONS

Suture tape augmentation of the MPFL resulted in similar primary contact pressures and joint kinematics in comparison with MPFL reconstruction using a tendon graft. A pretension of 2 N was found to restore the knee joint closest to normal patellofemoral kinematics.

Treatment of patellar dislocation with arthroscopic medial patellofemoral ligament reconstruction using gracilis tendon autograft and modified double-patellar tunnel technique: minimum 5-year patient-reported outcomes

BACKGROUND

The purpose of this study was to retrospectively analyze the clinical outcomes of patients with recurrent patellar dislocation who underwent arthroscopic medial patellofemoral ligament (MPFL) reconstruction using gracilis tendon autograft and a modified double-patellar tunnel method. We hypothesized that our modified method would provide good clinical outcomes.

METHODS

Patients who underwent arthroscopic MPFL reconstruction with autograft gracilis tendon and modified double-patellar tunnels technique for recurrent patellar dislocation and were followed up for a minimum of 5 years were identified, and the clinical and follow-up data were retrospectively analyzed. Preoperatively, joint hypermobility was assessed with the Beighton score. The Insall-Salvati ratio, TT-TG distance, and Q angle were measured on radiographic images. Patient-reported outcomes including the Kujala, Lysholm, and Tegner scores were collected preoperatively and postoperatively. Patient satisfaction was assessed at the end of 5 years. Complications and recurrent dislocation occurring after surgery were recorded.

RESULTS

A total of 79 patients (94 knees) were enrolled; of these, 13 (16.5%) were lost to follow-up. The data of 66 patients (80 knees) were available for final analysis. Mean age at surgery was 21.3 ± 7.8 years. Mean follow-up time was 66.1 ± 5.5 months (range, 60-78 months). Postoperative patient-reported outcome was not associated with Beighton score, Insall-Salvati ratio, or TT-TG distance. Q angle was negatively correlated to Kujala scores and Lysholm scores. Severity of trochlear dysplasia was not associated with postoperative patient-reported outcome. The mean Kujala score increased from 69.4 ± 7.9 to 96.1 ± 1.9, the mean Tegner score increased from 3.1 ± 1.3 to 5.9 ± 1.3, and the mean Lysholm score increased from 73.5 ± 14.6 to 95.3 ± 3.4. Two patients experienced recurrent patellar dislocation during follow-up.

CONCLUSIONS

MPFL reconstruction using autologous gracilis tendon under arthroscopy appears to be a reliable and safe method for treating recurrent patellar dislocation.

LEVEL OF EVIDENCE

Level IV.

Current concepts in the surgical management of patellar instability

BACKGROUND

Patellar instability is a common condition, and recurrent instability can be highly disabling. It is important to understand the patho-anatomy of patellar instability in order to treat it effectively, with the trochlear shape, patellar height and the integrity of the medial retinaculum being the most important factors in determining the risk of ongoing instability.

CLINICAL ASSESSMENT AND RADIOGRAPHIC ASSESSMENT

Clinical assessment is based around correct diagnosis of instability, identification of at risk features and an assessment of neuromuscular control and factors that may affect the potential for rehabilitation before or after surgery. Radiology is important to assess features predisposing to instability and to determine the best treatment plan for each individual.

TREATMENT

There are a range of surgical options for the treatment of patellar instability and these should be chosen based on an each patients individual patho-anatomy. Lateral release is not recommended as a treatment for patellar instability. Medial patello-femoral ligament reconstruction, tibial tubercle distalisation, trochleoplasty or occasionally tibial or femoral osteotomies for correction of rotational or coronal plane mal-alignment may all be used either individually or in combination. High quality physiotherapy is an essential part of post-operative management and should address the whole of the kinetic chain, working on strength and control of the lower limbs to optimise balance and movement patterns in order to achieve the best results.

When does the patella dislocate? A systematic review of biomechanical & kinematic studies

Background

Patellar dislocations are a significant injury with the potential for long term problems. Little work has been done on establishing the mechanism by which this injury occurs.

Objectives

To determine the mechanism of injury of a patella dislocation based on the available published literature and compare them to already proposed theories.

Methods

A systematic review of the literature was conducted following searches performed on MEDLINE, EMBASE and ProQuest from the earliest year of indexing using the following search terms in any combination: "patella", "dislocation", "mechanism of injury", "anatomy", "biomechanical" and "risk factor". A broad inclusion criteria was used that included studies that looked at patellar dislocations and instability with respect to the patellofemoral joint (PFJ) kinematics or altered kinematics of the PFJ. Studies that did not address the kinematics or biomechanics of the PFJ were excluded. Studies were appraised based on their methodology using a combination of the Critical Appraisal Skills Programme tool and the Quality Appraisal for Cadaveric Studies.

Results

113 studies were identified from a search of MEDLINE, EMBASE and ProQuest databases. Following application of our inclusion criteria, a total of 23 studies were included in our review. 18 of these studies were cadaveric biomechanical studies. The remaining studies were anatomical, imaging based, and a computer simulation based study.

Conclusions

These biomechanical and kinematic studies provide some evidence that a dislocation is likely to occur during early knee flexion with external rotation of the tibia and contraction of the quadriceps. There is limited evidence to support other elements of proposed mechanisms of dislocation.

Clinical Outcomes and Predictive Factors for Failure With Isolated MPFL Reconstruction for Recurrent Patellar Instability: A Series of 211 Reconstructions With a Minimum Follow-up of 3 Years

BACKGROUND

Reconstruction of the medial patellofemoral ligament (MPFL) is widely acknowledged as an integral part of the current therapeutic armamentarium for recurrent patellar instability. The procedure is often performed with concomitant bony procedures, such as distalization of the tibial tuberosity or trochleoplasty in the case of patella alta or high-grade trochlear dysplasia, respectively. At the present time, few studies have evaluated the clinical effectiveness of MPFL reconstruction as an isolated intervention.

PURPOSE

To report the clinical outcomes of isolated MPFL reconstruction in cases of patellar instability and to identify predictive factors for failure.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A retrospective analysis of prospectively collected data was performed, including all patients who had undergone isolated MPFL reconstruction between January 2008 and January 2014. Preoperative assessment included the Kujala score, assessment of patellar tracking ("J-sign"), and radiographic features, such as trochlear dysplasia according to Dejour classification, patellar height with the Caton-Deschamps index (CDI), tibial tubercle-trochlear groove distance, and patellar tilt. The Kujala score was assessed postoperatively. Failure was defined by a postoperative patellar dislocation or surgical revision for recurrent patellar instability.

RESULTS

A total of 239 MPFL reconstructions were included; 28 patients (11.7%) were uncontactable and considered lost to follow-up. Thus, 211 reconstructions were analyzed with a mean follow-up of 5.8 years (range, 3-9.3 years). The mean age at surgery was 20.6 years (range, 12-48 years), and 55% of patients were male. Twenty-seven percent of patients had a preoperative positive J-sign, and 93% of patients had trochlear dysplasia (A, 47%; B, 25%; C, 15%; D, 6%). The mean CDI was 1.2 (range, 1.0-1.7); mean tibial tubercle-trochlear groove distance, 15 mm (range, 5-30 mm); and mean patellar tilt, 23° (range, 9°-47°). The mean Kujala score improved from 56.1 preoperatively to 88.8 ( P < .001). Ten failures were reported that required surgical revision for recurrent patellar instability (4.7%). Uni- and multivariate analyses highlighted 2 preoperative risk factors for failure: patella alta (CDI ≥1.3; odds ratio, 4.9; P = .02) and preoperative positive J-sign (odds ratio, 3.9; P = .04).

CONCLUSION

In cases of recurrent patellar instability, isolated MPFL reconstruction would appear to be a safe and efficient surgical procedure with a low failure rate. Preoperative failure risk factors identified in this study were patella alta with a CDI ≥1.3 and a preoperative positive J-sign.

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

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

Biomechanical Analysis of Tibial Tuberosity Medialization and Medial Patellofemoral Ligament Reconstruction

Biomechanical studies are commonly performed to evaluate the influence of medial patellofemoral ligament (MPFL) reconstruction and tibial tuberosity medialization on patellar tracking and patellofemoral contact pressures. The most common method is in vitro simulation of knee function, but computational simulation of knee function and computational reconstruction of in vivo motion can also be utilized. The current review of the biomechanical literature indicates that MPFL reconstruction and tibial tuberosity medialization reduce lateral patellar tracking. Decreased lateral patellofemoral contact pressures have also been noted. For MPFL reconstruction, the most commonly noted biomechanical concerns are graft overtensioning and nonanatomic attachment on the femur leading to overconstraint of the patella and elevated medial contact pressures. For tuberosity medialization, the influence of altered tibiofemoral kinematics on postoperative function is unknown. Future biomechanical studies should emphasize inclusion of anatomic features and tracking patterns related to patellar instability, with comparison between the surgical approaches for continued development of treatment guidelines.

Medial Patellofemoral Ligament Reconstruction: Impact of Knee Flexion Angle During Graft Fixation on Dynamic Patellofemoral Contact Pressure-A Biomechanical Study

PURPOSE

Objective evaluation of the optimal graft tension angle to fully restore patellofemoral contact pressure in reconstruction of the medial patellofemoral ligament (MPFL) in comparison to the native knee.

METHODS

Twelve cadaveric knee specimens were fixed in a custom-made fixation device. A sensitive pressure film (Tekscan) was fixed in the patellofemoral joint, and patellofemoral contact pressure was assessed during a dynamic flexion movement from 0° to 90°. The MPFL was cut and measurements were repeated. Reconstruction of the MPFL was performed with the gracilis tendon subsequently fixed in the femur at 15°, 30°, 45°, 60°, 75°, and 90° of knee flexion under controlled tension (2 N). The sequence of the flexion angles was alternated. Pressure measurements were repeated after every fixation of the graft.

RESULTS

No significant differences were seen in the overall patellofemoral contact pressure compared to the native knee (P > .05). However, medial patellofemoral pressure showed a significant increased patellofemoral contact pressure after MPFL reconstruction at a knee flexion angle during graft fixation of 15° (P = .027), 45° (P = .050, P = .044), and 75° (P = .039). Moreover, proximal/distal patellofemoral contact pressure revealed a significantly reduced contact pressure at 15° (P = .003), 30° (P = .009), 45° (P = .025), 75° (P = .021), and 90° (P = .022) of flexion distal after MPFL reconstruction compared with the intact knee. Lateral patellofemoral contact pressure was significantly reduced in all performed reconstructions (P < .05).

CONCLUSIONS

The flexion angle during graft fixation for MPFL reconstruction did not have a significant impact on the overall patellofemoral contact pressure. However, selective medial, proximal, distal, and lateral patellofemoral contact pressure was significantly altered for all reconstructions. Fixation of the MPFL graft at 60° of flexion was able to most closely restore patellofemoral contact pressure compared with the intact knee.

CLINICAL RELEVANCE

Based on the findings of the present study, fixation of the graft in anatomic reconstruction of the MPFL should be considered in 60° of flexion under low tension (2 N) to most closely restore patellofemoral contact pressure compared with the native knee.

Medial patellotibial ligament and medial patellomeniscal ligament: anatomy, imaging, biomechanics, and clinical review

PURPOSE

The purpose of this article is to review anatomical, biomechanical, and clinical data of the medial patellotibial ligament (MPTL) and medial patellomeniscal ligament (MPML), as well as studies focusing on the medial patellofemoral ligament (MPFL) but with relevant data about the MPTL and MPML.

METHODS

A literature search of articles specifically addressing the MPTL and/or MPML was included along with studies focusing on the MPFL but with relevant data about the MPTL and MPML.

RESULTS

The medial patellar ligaments responsible for maintaining the stability of the patellofemoral (PF) joint include the MPFL, the MPTL, and the MPML. The MPFL is considered the primary restraint to lateral patellar translation, while the latter two are considered secondary restraints. There is robust literature on the anatomical, imaging, and biomechanical characteristics of the MPFL, and also the clinical outcome of its injury and surgical reconstruction; much less is known about the MPTL and MPML. Isolated MPFL reconstruction has good clinical and functional outcomes, with a low failure rate when defined as frank re-dislocation. Complications, including continued episodes of patellar apprehension and subluxation, remain present in most series. In addition, the current literature primarily includes a homogeneous population with few excessive anatomic dysplastic factors. There is lack of knowledge on the role of MPTL and MPML in (potentially) aiding patella stabilization and improving clinical outcomes. Understanding the role of the medial-sided patellar ligaments, in particular the role of the secondary stabilizers, in PF function and injury will aid in this goal.

CONCLUSION

MPTL and MPML have consistent basic science literature, as well as favorable clinical outcomes of surgical patellar stabilization with reconstruction of the MPTL. However, there is much heterogeneity among clinical case series and lack of comparative studies to allow clear indication for the role of isolated or combined surgical reconstruction in patellar stabilization. Therefore, this comprehensive review helps understand the current knowledge and the possible applications in the orthopedic clinical practice.

LEVEL OF EVIDENCE

V.

Patellar tracking after isolated medial patellofemoral ligament reconstruction: dynamic evaluation using computed tomography

PURPOSE

Medial patellofemoral ligament (MPFL) reconstruction offers good clinical results with a very low rate of instability recurrence. However, its in vivo effect on patellar tracking is not clearly known. The aim of this study is to investigate the effects of MPFL reconstruction on patellar tracking using dynamic 320-detector-row CT.

METHODS

Ten patients with patellofemoral instability referred to isolated MPFL reconstruction surgery were selected and subjected to dynamic CT before and ≥6 months after surgery. Patellar tilt angles and shift distance were analysed using computer software specifically designed for this purpose. Kujala and Tegner scores were applied, and the radiation of the CTs was recorded. Two protocols for imaging acquisition were compared: a tube potential of 80 kV and 50 mA versus a tube potential of 120 kV and 100 mA, both with a slice thickness of 0.5 mm and an acquisition duration of 10 s.

RESULTS

There were no changes in patellar tracking after MPFL reconstruction. There was no instability relapse. Clinical scores improved from a mean of 51.9 (±15.6)-74.2 (±20.9) on the Kujala scale (p = 0.011) and from a median of 2 (range 0-4) to 4 (range 1-6) on the Tegner scale (p = 0.017). The imaging protocols produced a dose-length product (DLP) of 254 versus 1617 mGycm and a radiation effective estimated dose of 0.2 versus 1.3 mSv, respectively. Both protocols allowed the analysis of the studied parameters without loss of precision.

CONCLUSIONS

Reconstruction of the MPFL produced no improvement in patellar tilt or shift in the population studied. The low-radiation protocol was equally effective in measuring changes in patellar tracking and is recommended. Although the procedure successfully stabilized the patella, knee surgeons should not expect patellar shift and tilt correction when performing isolated patellofemoral ligament reconstruction in patients with recurrent patellar instability.

LEVEL OF EVIDENCE

IV.

Editorial Commentary: The Medial Patellar Ligaments: A Step Closer to the Knee Surgeon's "Rubik's Cube" Solution

Recent cadaveric research analyzing the medial patellar ligaments and their contribution to patellar stability points out not only the need for reconstruction of the medial patellofemoral ligament, but also the medial tibiofemoral ligament to restore normal patellar stability and biomechanics.

Biomechanical evaluation of MPFL reconstructions: differences in dynamic contact pressure between gracilis and fascia lata graft

PURPOSE

To evaluate the knee kinematics of the intact, MPFL-ruptured and MPFL-reconstructed knee and, moreover, to compare dynamic patellofemoral contact pressure of the gracilis tendon and the fascia lata as an alternative graft option for reconstruction of the MPFL.

METHODS

Eight paired human cadaveric knees were fixed in a custom-made fixation device. Patellofemoral contact pressure was assessed during a dynamic flexion movement at 15°-30°-45°-60°-75° and 90° using a pressure-sensitive film (Tekscan). The medial patellofemoral ligament was cut, and measurements were repeated. Finally, reconstruction of the MPFL was performed using the gracilis tendon (group I) or a fascia lata graft (group II). Tunnel localization was performed under fluoroscopic control. Grafts were fixed at 30° of flexion, and pressure measurements were repeated.

RESULTS

Incision of the medial patellofemoral ligament significantly reduced patellofemoral contact pressure at 15°, 30° and 45° of knee flexion compared to the intact knee (p < 0.05), whereas reconstruction of the MPFL using either gracilis tendon of the fascia lata was able to restore pressure distributions at 15° and 30° of knee flexion. However, in the hamstring group, reconstruction of the MPFL revealed a significantly reduced contact pressure at 45° of flexion (p = 0.038) compared to the intact knee. In the fascia lata group, a significant reduction in patellofemoral contact pressure was observed after MPFL reconstruction at 45°, 60°, 75° and 90° of knee flexion (p < 0.05).

CONCLUSIONS

Anatomic reconstruction of the MPFL with either a gracilis or a fascia lata graft showed comparable patellofemoral pressure distributions which were closely restored compared to the native knee. Therefore, the fascia lata has shown to be a viable alternative to the gracilis tendon for reconstruction of the MPFL. However, anatomic reconstruction of the MPFL may lead to persistently altered patellofemoral contact pressure during knee flexion compared to the native knee independent of the tested graft.

The patellofemoral joint: from dysplasia to dislocation

Patellofemoral dysplasia is a major predisposing factor for instability of the patellofemoral joint. However, there is no consensus as to whether patellofemoral dysplasia is genetic in origin, caused by imbalanced forces producing maltracking and remodelling of the trochlea during infancy and growth, or due to other unknown and unexplored factors.The biomechanical effects of patellofemoral dysplasia on patellar stability and on surgical procedures have not been fully investigated. Also, different anatomical and demographic risk factors have been suggested, in an attempt to identify the recurrent dislocators. Therefore, a comprehensive evaluation of all the radiographic, MRI and CT parameters can help the clinician to assess patients with primary and recurrent patellar dislocation and guide management.Patellofemoral dysplasia still represents an extremely challenging condition to manage. Its controversial aetiology and its complex biomechanical behaviour continue to pose more questions than answers to the research community, which reflects the lack of universally accepted guidelines for the correct treatment. However, due to the complexity of this condition, an extremely personalised approach should be reserved for each patient, in considering and addressing the anatomical abnormalities responsible for the symptoms. Cite this article: EFORT Open Rev 2017;2. DOI: 10.1302/2058-5241.2.160081. Originally published online at www.efortopenreviews.org.

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.

Knee biomechanics during walking in recurrent lateral patellar dislocation are normalized by 1 year after medial patellofemoral ligament reconstruction

PURPOSE

Gait kinematics and kinetics of the knee before and after medial patellofemoral ligament (MPFL) reconstruction in patients with recurrent lateral patellar dislocation (RPD) are unknown. The purpose of this study was to measure knee kinematics and kinetics during gait before and 1 year after anatomical MPFL reconstruction in patients with RPD and compare the results to healthy individuals.

METHODS

Eleven RPD patients were treated using an anatomical MPFL reconstruction procedure. Gait analysis was conducted before and at 3, 6, and 12 months after surgery. For comparison, 15 healthy volunteers with no history of orthopaedic problems in their lower limbs were included as the control group. Knee kinematics and kinetics were analysed during gait.

RESULTS

Before surgery, the internal knee extension moment in RPD patients was significantly lower than in controls (P = 0.025). At 3 months post-operatively, there was an additional decrease in knee extension moment compared to before surgery, and so it was still significantly lower than in the control group (P < 0.01). One year post-operatively, knee extension moment in the RPD group was significantly increased compared to 3 months post-operatively (P < 0.01). The knee flexion angle in the early stance phase in the RPD group at 3 months post-operatively was significantly lower than that of controls (P < 0.01). Knee kinematics and kinetics were similar to that of controls 1 year after surgery.

CONCLUSION

Initially, RPD patients had lower knee extension moments during gait compared with controls, but by 1 year after MPFL reconstruction, knee kinematics and kinetics of gait in the RPD patients had returned to normal. These observations indicate that MPFL reconstruction may help to delay prospective knee OA as long as possible by restoring the conformation of the patellofemoral joint and gait biomechanics by surgery.

Reconstruction of the medial patellofemoral ligament using autologous graft from quadriceps tendon to treat recurrent patellar dislocation

OBJECTIVE

The objective of this study was to evaluate the efficacy of the surgical technique using the quadriceps tendon as a graft in static reconstruction of the medial patellofemoral ligament.

METHODS

This was a prospective case series study in which the participants were 22 patients with a diagnosis of recurrent patellar dislocation without any other anatomical alterations that required surgical treatment. The functional results from the technique were evaluated using clinical data and the Lysholm questionnaire, one year after the operation.

RESULTS

It was observed that the patients were predominantly female (86%) and under 21 years of age (73%), just like in the literature. At the first annual return after the surgery, there was no significant pain on medium efforts, no loss of range of motion and a positive apprehension test. According to the questionnaire used, the results were graded as good. The patients who reported having severe pain on greater effort were involved in employment-related legal disputes.

CONCLUSION

This technique showed low morbidity and good functional results over the short term.

The triangle zone as a femoral attachment location in medial patellofemoral ligament reconstruction: An in vivo three-dimensional analysis using an open MRI scanner

BACKGROUND

The exact isometric points for medial patellofemoral ligament (MPFL) fixation during MPFL reconstruction remain a matter of debate.

PURPOSE

The aim of this study was to characterize the functional length changes of various patellar and femoral fixation sites using in vivo three-dimensional (3D) movement patterns and to determine the ideal fixation sites at which the graft remains largely isometric.

METHODS

Twelve right knees of healthy volunteers were examined at early flexion angles (0°, 10°, 20°, 30°, 40°, 50°, and 60°) with a horizontal-type open magnetic resonance scanner, and 3D models were reconstructed using the marching cubes algorithm. Six points on the femoral condyle and three points on the medial aspect of the patella were simulated. The matching points represented the MPFL, which crossed the bony obstacle. The MPFL length changes were analyzed at various flexion degrees.

RESULTS

The lengths from the dome of Blumensaat's line (G), the point 10mm inferior to the adductor tubercle (H), to the midpoint between the adductor tubercle and the medial epicondyle (I) were more isometric than other points. The lengths between the dome of Blumensaat's line and the superior pole of the patella changes significantly between 20° and 60° of flexion (p=0.040).

CONCLUSIONS

The femoral fixation site may be more accurately located during MPFL reconstruction at the G, H, and I points to restore the native biomechanical function of the MPFL. The dome of Blumensaat's line should be avoided during MPFL reconstruction with the superficial quad technique.

CLINICAL RELEVANCE

A triangular region composed of the dome of Blumensaat's line, 10mm inferior to the adductor tubercle, and the midpoint between the adductor tubercle and medial epicondyle is recommended as the femoral fixation site.

Sequential 3D analysis of patellofemoral kinematics from biplanar x-rays: In vitro validation protocol

BACKGROUND

Developing criteria for assessing patellofemoral kinematics is crucial to understand, evaluate, and monitor patellofemoral function. The objective of this study was to assess a sequential 3D analysis method based on biplanar radiographs, using an in vitro protocol.

HYPOTHESIS

Biplanar radiography combined with novel 3D reconstruction methods provides a reliable evaluation of patellofemoral function, without previous imaging.

MATERIAL AND METHODS

Eight cadaver specimens were studied during knee flexion cycles from 0° to 60° induced by an in vitro simulator. The protocol was validated by investigating sequential and continuous motion using an optoelectronic system, evaluating measurement accuracy and reproducibility using metallic beads embedded in the patella, and comparing the 3D patellar geometry to computed tomography (CT) images.

RESULTS

The differences in position between the sequential and continuous kinematic analyses were less than 1mm and 1°. The protocol proved reliable for tracking several components of knee movements, including patellar translations, flexion, and tilt. In this analysis, uncertainty was less than 2 mm for translations and less than 3° for rotations, except rotation in the coronal plane. For patellar tilt, uncertainty was 5°. Mean difference in geometry was 0.49 mm.

DISCUSSION

Sequential analysis results are consistent with continuous kinematics. This analysis method provides patellar position parameters without requiring previous CT or magnetic resonance imaging. A clinical study may deserve consideration to identify patellofemoral kinematic profiles and position criteria in vivo.

LEVEL OF EVIDENCE

IV, experimental study.

The ability of medial patellofemoral ligament reconstruction to correct patellar kinematics and contact mechanics in the presence of a lateralized tibial tubercle

BACKGROUND

Tibial tubercle (TT) transfer and medial patellofemoral ligament (MPFL) reconstruction are used after patellar dislocations. However, there is no objective evidence to guide surgical decision making, such as the ability of MPFL reconstruction to restore normal behavior in the presence of a lateralized TT.

HYPOTHESIS

MPFL reconstruction will only restore joint contact mechanics and patellar kinematics for TT-trochlear groove (TG) distances up to an identifiable limit.

STUDY DESIGN

Controlled laboratory study.

METHODS

Eight fresh-frozen cadaveric knees (mean TT-TG distance, 10.4 mm) were placed on a testing rig. Individual quadriceps heads and the iliotibial band were loaded with 205 N in physiological directions using a weighted pulley system. Patellofemoral contact pressures and patellar tracking were measured at 0°, 10°, 20°, 30°, 60°, and 90° of flexion using pressure-sensitive film and an optical tracking system. The MPFL attachments were marked. TT osteotomy was performed, and a metal T-plate was fixed to the anterior tibia with holes at 5-mm intervals for TT fixation. The anatomic TT position was restored after plate insertion. The TT was lateralized in 5-mm intervals up to 15 mm, with pressure and tracking measurements recorded. The MPFL was transected and all measurements repeated before and after MPFL reconstruction using a double-stranded gracilis tendon graft. Data were analyzed using repeated-measures ANOVA, Bonferroni post hoc analysis, and paired t tests.

RESULTS

MPFL transection significantly elevated lateral patellar tilt and translation and reduced mean medial contact pressures during early knee flexion. These effects increased significantly with TT lateralization. MPFL reconstruction restored patellar translation and mean medial contact pressures to the intact state when the TT was in anatomic or 5-mm lateralized positions. However, these were not restored when the TT was lateralized by 10 mm or 15 mm. Patellar tilt was restored after 5-mm TT lateralization but not after 10-mm or 15-mm lateralization.

CONCLUSION

Considering the mean TT-TG distance in this study (10.4 mm), findings suggest that in patients with TT-TG distances up to 15 mm, patellofemoral kinematics and contact mechanics can be restored with MPFL reconstruction. However, for TT-TG distances greater than 15 mm, more aggressive surgery such as TT transfer may be indicated.

CLINICAL RELEVANCE

This provides guidance to surgeons as to the threshold at which MPFL reconstruction may satisfactorily restore patellofemoral mechanics, beyond which more invasive surgery such as TT transfer may be indicated.

Anatomy of the Medial Patello-Femoral Ligament: a systematic review of the last 20 years literature

BACKGROUND

Although many studies have investigated the anatomy of the Medial Patello-Femoral Ligament (MPFL), some studies have even questioned its existence. In the last 20 years, there is a renewed interest on the role of the MPFL in patello-femoral instability. As a result, several studies have been published that describe the anatomy, function and possible surgical reconstruction of the MPFL. Despite the large amount of literature produced, there is still a lack of consensus on what is its real anatomy as there are currently no systematic reviews on this topic.

PURPOSES

Thus, the aim of this review is to systematically report the results in literature regarding in anatomical papers, the existence, size, insertion sites and relationships of this ligament with the other medial structures of the knee.

METHODS

We have systematically analyzed anatomical studies currently available in literature between 1980 and December 2012. The search was carried out on Medline, Embase, Cochrane Library and Google Scholar. We checked reference lists of articles, reviews and textbooks identified by the search strategy for other possible relevant studies.

RESULTS

The outcomes examined are the presence of the ligament, its size (length, width, thickness), and its patellar and femoral insertions. A total of 312 cadaveric knees were included in the 17 studies; the MPFL was identified in 99% of cases (309).

CONCLUSIONS

The consensus is that the MPFL is almost always present in the dissected knees. The size and insertions of the ligament demonstrate great variation between cadavers.

LEVEL OF EVIDENCE

Systematic review of anatomical study, Level 1.

Lateral patellar facetectomy and medial reefing in patients with lateral facet syndrome after patellar-retaining total knee arthroplasty

We analyzed clinical outcomes of partial lateral patellar facetectomy and medial reefing in patients with lateral patellar facet syndrome with painful patellar-retaining total knee arthroplasty. 34 patients were followed for a mean of 40 months. All 34 patients were matched with those having secondary patellar resurfacing without facetectomy. Both groups experienced significant pain relief and range of motion improvement. The facetectomy group had higher Kujala scores than those in patellar resurfacing group. Patients with facetectomy had significantly less pain postoperatively. There were significant differences in postoperative lateral patellar tilt and congruency angle in both groups. The mid-term results for LPF with medial reefing are promising to resolve pain in patients with lateral patellar facet syndrome in patellar-retaining TKA. Therapeutic level III (retrospective comparative study).

Shape and size of the medial patellofemoral ligament for the best surgical reconstruction: a human cadaveric study

PURPOSE

The aim of this study was to investigate the shape and the attachments of the medial patellofemoral ligament (MPFL) in cadaver specimens to determine an anatomical basis for the best MPFL reconstruction.

METHODS

Twenty fresh-frozen knees were used. Dissection protocol implied performing dissections from within the knee joint. We investigated the shape and the attachments between the MPFL and the quadriceps tendon, the patellar and femur insertions, and all the other relationships with the medial soft tissues of the knee.

RESULTS

The distal fibers of MPFL were interdigitated with the deep layer of the medial retinaculum. All isolated ligament had a sail-like shape with the patellar side bigger than the femoral side. The femoral insertion, distinct both from medial epicondyle and adductor tubercle, was located at 9.5 mm (range 4-22) distal and anterior respect to adductor tubercle and proximal and posterior to epicondyle. The medial third of the thickness of patella was involved in the insertion. The proximal third of the patella is always involved in the MPFL attachment; in 45% of the cases, it was extended to the medial third and in one case, an extension at the distal third was found. Additionally in 35% (7 cases), it extended to the quadriceps tendon and it were inconstantly attached at the vastus medialis obliques (VMO) tendon and at the vastus intermedius (VI) tendon in an aponeurotic structure.

CONCLUSIONS

The MPFL is a distinct structure that goes from patella to femur with a sail-like shape; its patellar insertion, that mostly occur via an aponeurosis tissue with VMO and VI, is at the proximal third of the patella but it may extend in some cases to the medial third patella or to the quadriceps tendon, or very rarely to the distal third of the patella. In the femoral side, the MPFL is inserted in its own site, in most cases distinct both from epicondyle and adductor tubercle, located on average at a 9.5 mm distance distally and anteriorly in respect to the adductor tubercle. Its lower margin was difficult to define. Given the importance of this structure, it must be reconstructed as anatomically as possible in its insertion and in its shape. Many attempts have been made to make functional reconstructions with less than excellent results.

Medial patellofemoral ligament reconstruction with bioactive synthetic ligament is an option. A 3-year follow-up study

PURPOSE

The purpose of this study was to evaluate mid-term follow-up results of medial patellofemoral ligament (MPFL) reconstruction using a bioactive synthetic ligament in the treatment of objective patellofemoral (PF) instability.

METHODS

Sixteen patients (18 knees) presenting with objective PF instability underwent a MPFL reconstruction, isolated or associated with other surgical procedures for PF stabilization. All patients were clinically evaluated at a minimum follow-up of 3 years. Kujala, subjective IKDC and KOOS scores were used to assess clinical outcome. Pre-operative and post-operative pain was quantified with VAS scale and the overall satisfaction graded according to Insall and Crosby. Although none of the patients in this series were involved in high-level sports activity because of patellofemoral instability, activity level pre-operatively and at follow-up were evaluated according to Tegner scale.

RESULTS

No recurrence of dislocation was observed in this series. The overall satisfaction rate was 88.8%. Kujala score improved significantly from 57±8.4 to 84.3±10.2 points (p<.01). Both subjective IKDC (42.4±7.13 to 70.1±3.9) and KOOS (62.7±4.34 to 82.8±8.8) significantly improved from pre-operative evaluation (p<.01). VAS decreased from a mean pre-operative value of 2.5±1.6 to 1.4±1.5 at 3 years follow-up. Only one patient required revision debridement surgery for persistent medial epicondylar pain.

CONCLUSIONS

Isolated or associated MPFL reconstruction with bioactive synthetic ligament is a valid option in surgical treatment of objective PF instability, with results at mid-term follow-up comparable to autologous graft, thus minimizing donor-site morbidity and associated complications.

LEVEL OF EVIDENCE

IV.

Simulation of the optimal femoral insertion site in medial patellofemoral ligament reconstruction

PURPOSE

To develop and validate a new simulation system to predict the optimal femoral insertion site of the medial patellofemoral ligament (MPFL) using preprogrammed conditions of graft length change.

METHODS

A computed tomography scan was performed for constructing bone surface models of the patella and the femur. Lateral radiographs of the knee and axial radiographs of the patellofemoral joint at knee flexion were used for constructing a three-dimensional patellofemoral joint model by 3D-2D image matching at each knee flexion angle. To determine the optimal femoral insertion site, the following three conditions were devised: (1) MPFL behaves isometric from 0° to 60°, (2) MPFL is most taut at full extension, and (3) MPFL is slack at more than 60° of knee flexion. Every condition was applied to the femoral bone surface model, and the area that fulfilled all three conditions was defined as the optimal femoral insertion site of MPFL. Twenty knees of ten healthy volunteers were assessed to verify the simulation. Comparison between simulated optimal femoral insertion and anatomical insertion was done.

RESULTS

The mean simulated optimal femoral insertion was close to the anatomical insertion site. There were no significant differences in the proximal-distal position and anterior-posterior position between the simulated insertion and the anatomical insertion sites.

CONCLUSION

The system can be useful for predicting the optimal femoral insertion site as a part of a preoperative plan for MPFL reconstruction, and it may help surgeons to determine the optimal femoral insertion site during MPFL reconstruction.

Minimally invasive medial patellofemoral ligament reconstruction with fascia lata allograft: surgical technique

The present paper describes a new minimally invasive anatomic medial patellofemoral ligament reconstruction, using a fascia lata allograft as graft source and arthroscopy to obtain balanced fixation throughout the range of motion.

Tibial Tuberosity Osteotomy: Indications, Techniques, and Outcomes

Tibial tuberosity osteotomy (TTO) is a well-described treatment option for a broad range of patellofemoral joint disorders, including patellofemoral instability, patellar and trochlear focal chondral lesions, and patellofemoral arthritis. The purpose of this article is to review the evolution of the TTO procedure, from the original Hauser procedure to the current anteromedialization procedure, as well as discuss the pertinent anatomy and radiographs that accompany this procedure. The article highlights the surgical techniques for some of the more commonly performed TTO procedures and discusses the outcomes of the various TTO techniques. Complications, as well as clinical pearls to avoid these complications, are also included.

Anatomical study of the medial patello-femoral ligament: landmarks for its surgical reconstruction

PURPOSE

The aim of this dissection study was to describe the anatomical insertions of the medial patello-femoral ligament (MPFL), and to assess its relationship with surrounding structures to improve its surgical reconstruction.

METHODS

Twelve knees (7 cadavers) were included for the study. Measurements and general features of the MPFL were assessed: lengths, widths and insertions.

RESULTS

The MPFL was found in all knees, presenting a triangular shape, and extending from the medial part of the patella to its femoral insertion (its length was of 59 ± 6.6 mm), distal to the adductor tubercle. The mean femoral insertion of the MPFL was 7.2 ± 2.7 mm proximal and 7.4 ± 4.0 mm posterior to the medial femoral epicondyle (MFE). It was also at a mean 11 ± 2.8 mm distal and 1.3 ± 2.1 mm posterior to the adductor tubercle, and 22 ± 6.4 mm anterior to the posterior condyle. We did not find any double-bundle organization on the patellar insertion. The width of the MPFL was 8.8 ± 2.9 mm at the femoral insertion, 27 ± 5.9 mm at the patellar insertion, and 12 ± 3.1 mm in the middle of the MPFL. The vastus medialis obliquus was found to be inserted on the superior part of the MPFL.

CONCLUSION

The adductor tubercle appeared to be a better landmark than the MFE for the femoral tunnel positioning during surgical reconstructions of the MPFL because it was easier to identify and its relationship with the femoral insertion of the MPFL was constant (10 mm below).

Are the tubular grafts in the femoral tunnel in an anatomical or isometric position in the reconstruction of medial patellofemoral ligament?

PURPOSE

The purpose of this study was to evaluate the biomechanical results from the in vitro reconstruction of medial patellofemoral ligament (MPFL) using a navigation-assisted technique on a cadaveric model and its effects on patellar stability and kinematics. The authors investigated the hypothesis that patellar kinematics after reconstruction with a tubular graft are not optimal when compared with the original fan-shaped MPFL.

METHODS

In six fresh-frozen cadaveric knees, lateral loads (25 N) were applied on the patella at 0°, 30°, 60° and 90° of knee flexion in three different MPFL states: intact, cut and reconstructed. The arrangement allowed positional measurements of patellar motion to be tracked in six degrees of freedom. Medial to lateral patellar translation and patellar tilt were recorded. The kinematics after a technique of MPFL reconstruction, performed with a gracilis tendon in a blind femoral tunnel guided by navigation, were compared against kinematics recorded in the MPFL intact state. A temporary fixation of adequate tension to engage the lateral patellar facet in extension was applied to the MPFL and, after graft cycling, the final fixation was done at 70° knee flexion with an interference screw.

RESULTS

There was a comparable medial to lateral patellar translation and tilting of the patella in the MPFL-intact and the MPFL-reconstructed state. Static patellar translation in the MPFL-reconstructed state, with and without the application of load, was comparable to patellar translation in the MPFL-intact state. The dynamic patellofemoral shift kinematics recorded an under-constraint in early flexion and over-constraint in late flexion, while an opposite effect was recorded in patellar tilt. However, these differences were not statistically significant.

CONCLUSION

The study confirmed the major role of the MPFL in case of medial loading between 0° and 60°, by focusing on the importance of kinematically identifying the proper femoral point for fixation. While the study demonstrates the importance of kinematic determination of the proper femoral point of fixation, as the anatomical insertion remains difficult to identify. Even in dissected cadavers, the authors recorded a slightly anterior placement than native MPFL. After reconstruction, patellar stability in terms of lateral translation and tilt was similar to the intact MPFL, but patellar kinematics were not optimal with the use of a smaller and tubular graft than the native wider and fan-shaped MPFL.

Comparison of 2 different techniques for anatomic reconstruction of the medial patellofemoral ligament: a prospective randomized study

BACKGROUND

The comparative clinical outcome of anatomic reconstruction of the medial patellofemoral ligament (MPFL) between the Y-graft technique and C-graft technique for chronic patellar instability is unknown.

HYPOTHESIS

Anatomic reconstruction of the MPFL with a Y-graft technique (a Y-shaped graft: femoral fixation first with separate tensioning of the 2 bundles) would yield better clinical results than a C-graft procedure (a C-shaped graft: patellar fixation first with simultaneous tensioning of both bundles) for chronic patellar instability.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 2.

METHODS

Ninety patients with symptomatic chronic patellar dislocations or instability were randomly divided into 2 groups to undergo double-bundle MPFL reconstruction either with the Y-graft technique or C-graft technique. Follow-ups were performed at 3, 6, 12, and 24 months postoperatively. The patellar stability was evaluated with the apprehension test at follow-up. The patellofemoral morphological characteristics were evaluated on axial computed tomography (CT) scans at 30° of knee flexion, and knee function was evaluated using the Lysholm and Kujala scores preoperatively and at 24 months postoperatively.

RESULTS

Forty patients in the Y-graft group and 42 patients in the C-graft group were followed for 24 months. No recurrent dislocation or subluxation was reported in either group. On CT scans, congruence angle, patellar tilt angle, lateral patellar angle, and lateral displacement were restored to the normal range. The mean postoperative Lysholm scores for the Y-graft group and C-graft group were 92.3 ± 3.9 and 88.4 ± 6.8, respectively (P = .001). The mean postoperative Kujala scores were 95.9 ± 4.7 and 91.3 ± 9.7 for the Y-graft group and C-graft group, respectively (P = .001), with a good or excellent rate of 97.5% in the Y-graft group compared with 83.3% in the C-graft group (P = .031).

CONCLUSION

With no patellar redislocations reported, the Y-graft technique for the double-bundle anatomic MPFL reconstruction achieved statistically better knee function than the C-graft procedure at a minimum 2-year follow-up. However, the increase was less than the minimal clinically important difference, and further research is required to demonstrate its meaningful clinical improvement.

Patellofemoral anatomy and biomechanics: current concepts

The patellofemoral joint, due to its particular bone anatomy and the numerous capsuloligamentous structures and muscles that act dynamically on the patella, is considered one of the most complex joints in the human body from the biomechanical point of view. The medial patellofemoral ligament (MPFL) has been demonstrated to contribute 60% of the force that opposes lateral displacement of the patella, and MPFL injury results in an approximately 50% reduction in the force needed to dislocate the patella laterally with the knee extended. For this reason, recent years have seen a growing interest in the study of this important anatomical structure, whose aponeurotic nature has thus been demonstrated. The MPFL acts as a restraint during motion, playing an active role under conditions of laterally applied stress, but an only marginal role during natural knee flexion. However, it remains extremely difficult to clearly define the anatomy of the MPFL and its relationships with other anatomical structures.