The effect of reconstruction of the medial patellofemoral ligament on patellar tracking

The 100 Top-Cited Articles on Medial Patellofemoral Ligament: A Bibliometric Analysis and Review

Background

The medial patellofemoral ligament (MPFL) has been investigated widely in the past 30 years, resulting in many research achievements in this field.

Purpose

To perform a comprehensive bibliometric analysis to evaluate the 100 top-cited articles on the MPFL.

Study Design

Cross-sectional study.

Methods

We searched the Scopus database in December 2022 using the terms "medial patellofemoral ligament" OR "MPFL." The search was confined to English-language articles, including technical notes, systematic reviews on clinical outcomes and/or complications, clinical studies, studies regarding complications, and basic science articles (either cadaveric or biomechanical); we excluded letters, case reports, personal opinions, guidelines, editorials, and narrative or other types of reviews. Analysis of the 100 top-cited articles was performed according to total number of citations, average citations per year (ACY), study type, country of origin, journal of publication, affiliated institution, and most published authors.

Results

The total number of citations was 16,358 (range of citations per article, 72-692). The majority of articles were published as clinical studies (54%), with cadaveric studies being the second most common (21%). Most studies originated in the United States (32%), with Japan (15%) and Germany (13%) following. The American Journal of Sports Medicine published the majority of the 100 top-cited articles (37/100; 6304 citations) as well as the 10 top-cited articles according to ACY (7/10; mean, 285.14 citations). The most prolific authors were Nomura (8 articles); Burks (6 articles); and Inoue, Sillanpää, and Dreyhaupt (5 articles each).

Conclusion

By analyzing the characteristics of the 100 top-cited articles, this study demonstrated that the MPFL is a growing and popular area of research, with the focus varying through timeline trends. Questions regarding MPFL anatomy, isometry, and biomechanics might have been answered adequately, but research regarding optimal fixation technique under various circumstances is still ongoing.

Medial patellofemoral ligament reconstruction: A review

INTRODUCTION

Reconstruction of the medial patellofemoral ligament (MPFL) is an effective surgical method for the treatment of lateral patellar instability. At present, there is not much controversies regarding the femoral attachment, however, the controversies regarding patellar attachment versus attachment, number of graft strands, tension, isometry and so on. The following electronic databases will be searched: PubMed, the Cochrane Library, Embase, Web of Science, Medline. We will consider articles published between database initiation and March 2021. MPFL in the subject heading will be included in the study. Language is limited to English. Research selection, data extraction, and research quality assessment were independently completed by 2 researchers.

CONCLUSIONS

MPFL reconstruction is a reliable technique for the treatment of patellofemoral instability. The Schöttle point is still the mainstream method for locating the femoral attachment, the patellar attachment for single-bundle is located at the junction of the proximal one third and the distal two third of the longitudinal axis of the patella. For double-bundles, one is located in the proximal one third of the medial patellar edge and another is in the center of the patellar edge. Meanwhile, the adjustment of graft tension during operation is very important.

Clinical Comparison of Medial Patellofemoral Ligament Reconstruction With or Without Tibial Tuberosity Transfer for Recurrent Patellar Instability

BACKGROUND

No clear guidelines or widespread consensus has defined a threshold value of tibial tuberosity-trochlear groove (TT-TG) distance for choosing the appropriate surgical procedures when additional tibial tuberosity osteotomy (TTO) should be added to augment medial patellofemoral ligament (MPFL) reconstruction for recurrent patellar instability.

PURPOSE

To compare the clinical outcomes between MPFL reconstruction and MPFL reconstruction with TTO for patients who have patellar instability with a TT-TG distance of 15 to 25 mm.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

We retrospectively analyzed 81 patients who underwent surgical treatment using either MPFL reconstruction or MPFL reconstruction with TTO for recurrent patellar instability with a TT-TG distance of 15 to 25 mm; the mean follow-up was 25.2 months (range, 12.0-53.0 months). The patients were divided into 2 groups: isolated MPFL reconstruction (iMPFL group; n = 36) performed by 2 surgeons and MPFL reconstruction with TTO (TTO group; n = 45) performed by another 2 surgeons. Clinical outcomes were assessed using the Kujala score, Knee injury and Osteoarthritis Outcome Score, and Tegner activity score. Radiological parameters, including patellar height, TT-TG distance, patellar tilt, and congruence angle were compared between the 2 groups. Functional failure based on clinical apprehension sign, repeat subluxation or dislocation, and subjective instability and complications was assessed at the final follow-up. We also compared clinical outcomes based on subgroups of preoperative TT-TG distance (15 mm ≤ TT-TG ≤ 20 mm vs 20 mm < TT-TG ≤ 25 mm).

RESULTS

All of the clinical outcome parameters significantly improved in both groups at the final follow-up (P < .001), with no significant differences between groups. The radiological parameters also showed no significant differences between the 2 groups. The incidence of functional failure was similar between the 2 groups (3 failures in the TTO group and 2 failures in the iMPFL group; P = .42). In the TTO group, 1 patient experienced a repeat dislocation postoperatively and 2 patients had subjective instability; in the iMPFL group, 2 patients had subjective instability. The prevalence of complications did not differ between the 2 groups (P = .410). In the subgroup analysis based on TT-TG distance, we did not note any differences in clinical outcomes between iMPFL and TTO groups in subgroups of 15 mm ≤ TT-TG ≤ 20 mm and 20 mm < TT-TG ≤ 25 mm.

CONCLUSION

MPFL reconstruction with and without TTO provided similar, satisfactory clinical outcomes and low redislocation rates for patients who had patellar instability with a TT-TG distance of 15 to 25 mm, without statistical difference. Thus, our findings suggest that iMPFL reconstruction is a safe and reliable treatment for patients with recurrent patellar dislocation with a TT-TG distance of 15 to 25 mm, without the disadvantages derived from TTO.

Medial Patellofemoral Ligament Reconstruction Using Suture Tape for Patellofemoral Joint Instability

Objective

To describe a surgical technique using suture tape for reconstruction of the medial patellofemoral ligament (MPFL). This technique restores the stability of the reconstructed ligament and has excellent postoperative outcomes.

Method

This is a retrospective analysis. From January 2016 to June 2018, 17 patients underwent MPFL reconstruction using high‐strength suture (FiberTape; Arthrex) augmentation, with at least 12 months of follow up. There were 11 female and 6 male patients. The mean age at the time of MPFL reconstruction was 22.1 years (range 13–34 years). Clinical outcomes included pain level, knee range of motion, passive patellar hypermobility, and maltracking at follow‐up. The lateral patellofemoral angles, congruence angles, and patellar tilt angles were measured in a skyline view by CT at 30° of knee flexion at 12 months. Functional outcomes were assessed using the Lysholm knee scoring scale, the SF‐12 score, the Tegner score, and the Crosby and Insall grading system at yearly follow‐up.

Result

No patients were lost at the last follow up. One patient had recurrence of patellar dislocation and none of the others had serious complications. The success rate of MPFL repair for preventing recurrent dislocations was 94.1% (16 of 17 knees). Fifteen knees had full range of motion of more than 130°. At follow‐up, 2 knees were judged to have mild hypermobility and none had severe hypermobility or maltracking. Using the Crosby and Insall grading system, 12 knees (70.6%) were graded as excellent, 4 knees (23.5%) as good, 1 knee (5.9%) as fair to poor, and none as worse at the last follow‐up assessment. In all patients, the Lysholm knee score (55.12 ± 13.52 vs 79.88 ± 7.50, P < 0.01), the SF‐12 score (47 ± 9.53 vs 65.24 ± 12.82, P < 0.01), and the Tegner score (2.76 ± 1.39 vs 6.53 ± 1.70, P < 0.01) had improved at their 12‐month follow up. Compared with preoperative radiological findings, there was a significant improvement in lateral patellofemoral angle (−10.24 ± 7.10 vs 6 ± 5.43, P < 0.01), patellar tilt angle (26.53 ± 7.23 vs 9.88 ± 4.24, P < 0.01), and congruence angle (29.59 ± 11.95 vs −8.65 ± 4.86, P < 0.01).

Conclusion

The use of FiberTape in MPFL reconstruction can improve the stability of the knee following surgery and has good midterm clinical results and low complication rates.

Assessment and Trends of the Methodological Quality of the Top 50 Most Cited Articles on Patellar Instability

Background

Studies with a low level of evidence (LOE) have dominated the top cited research in many areas of orthopaedics. The wide range of treatment options for patellar instability necessitates an investigation to determine the types of studies that drive clinical practice.

Purpose

To determine (1) the top 50 most cited articles on patellar instability and (2) the correlation between the number of citations and LOE or methodological quality.

Study Design

Cross-sectional study.

Methods

The Scopus and Web of Science databases were assessed to determine the top 50 most cited articles on patellar instability between 1985 and 2019. Bibliographic information, number of citations, and LOE were collected. Methodological quality was calculated using the Modified Coleman Methodology Score (MCMS) and the Methodological Index for Non-Randomized Studies (MINORS). Mean citations and mean citation density (citations per year) were correlated with LOE, MCMS, and MINORS scores.

Results

Most studies were cadaveric (n = 10; 20.0%), published in the American Journal of Sports Medicine (n = 13; 26.0%), published between 2000 and 2009 (n = 41; 82.0%), and conducted in the United States (n = 17; 34.0%). The mean number of citations and the citation density were 158.61 ± 59.53 (range, 95.5-400.5) and 12.74 ± 5.12, respectively. The mean MCMS and MINORS scores were 59.62 ± 12.58 and 16.24 ± 3.72, respectively. No correlation was seen between mean number of citations or citation density versus LOE. A significant difference was found in the mean LOE of articles published between 1990 and 1999 (5.0 ± 0) versus those published between 2000 and 2009 (3.12 ± 1.38; P = .03) and between 2010 and 2019 (3.00 ± 1.10; P = .01).

Conclusion

There was a shift in research from anatomy toward outcomes in patellar instability; however, these articles demonstrated low LOE and methodological quality. Higher quality studies are necessary to establish informed standards of management of patellar instability.

[Optimization location of femoral attachment in medial patellofemoral ligament reconstruction assisted with arthroscopy for patellar dislocation]

Objective

To investigate the technique of optimizing the location of femoral attachment in medial patellofemoral ligament (MPFL) reconstruction assisted with arthroscopy and evaluate the effectiveness.

Methods

Between January 2014 and September 2018, 35 patients with patellar dislocation were admitted. There were 14 males and 21 females with an average age of 22.6 years (range, 16-38 years). All patients had a history of knee sprain. The disease duration ranged from 1 to 7 days (mean, 2.8 days). Patellar dislocation occurred 2-4 times (mean, 2.5 times). The preoperative Lysholm score and Kujala score were 47.60±11.24 and 48.37±9.79, respectively. The patellar congruence angle was (31.40±6.81)°, the patellar tilt angle was (29.95±5.44)°, the lateral patellofemoral angle was (-11.46±5.18)°, and the tibial tubercle-trochlear groove distance was (16.66±1.28) mm. All patients were treated by MPFL reconstruction with the semitendinosus tendon under arthroscopy. During operation, the suture anchors were inserted into the midpoint and the 1/3 point of superomedial edge of the patella. Then, the femoral tunnels were created in medial femoral condyle through limited excision. For tendon fixation, the Kirschner wires were inserted into adductor tubercle, medial epicondyle of femur, and the midpoint between the two points, as well as the anteriorly and posteriorly. Afterwards, the changes of ligament length and tension, patellar tracking, and the relationship of patella and femoral trochlea were evaluated, thereby determining the optimized femoral attachment for MPFL reconstruction. Finally, the patellar congruence angle, patellar tilt angle, and lateral patellofemoral angle were measured by imaging to assess the relationship of patella and femoral trochlea. Moreover, Lysholm score and Kujala score were used to evaluate the knee joint function.

Results

All incisions healed by first intention without infection. All patients were followed up 12-18 months (mean, 15.4 months). At 12 months, the Lysholm score was 94.40±3.99 and the Kujala score was 92.28±4.13, which were significant higher than those before operation ( P<0.05). No patellar dislocation occurred during follow-up. At 12 months, the patellar congruence angle was (6.57±4.59)°, the patellar tilt angle was (9.73±2.82)°, the lateral patellofemoral angle was (7.14±4.63)°, which were superior to those before operation ( P<0.05).

Conclusion

During the MPFL reconstruction under arthroscopy, a higher positioning accuracy for the femoral attachment and satisfactory effectiveness can be obtained by evaluating MPFL length and tension, patellofemoral joint kinematics, and patellar tracking.

Small, Short, Oblique Patellar Tunnels for Patellar Fixation Do Not Increase Fracture Risk or Complications in MPFL Reconstruction: A Retrospective Cohort Study

BACKGROUND

Large (4.5 mm) and/or transpatellar bone tunnels have been associated with patellar fracture after medial patellofemoral ligament (MPFL) reconstruction. To avoid this outcome, many surgeons now employ suture anchors to affix the MPFL graft to the patella.

PURPOSE

To evaluate the risk of patellar fracture and other outcomes associated with smaller (3.2-mm), short, oblique patellar tunnels as compared with suture anchor fixation in MPFL reconstruction.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A single institution's electronic medical record was queried for all patients undergoing MPFL reconstruction between March 2010 and December 2018. A chart review of operative reports was utilized to identify those who had undergone MPFL reconstruction. Patients undergoing revision MPFL reconstruction or reconstruction with fully transpatellar bone tunnels were excluded. The incidence of patellar fracture and outcomes were evaluated from chart review. The mean duration of follow-up was >2 years.

RESULTS

A total of 384 knees in 352 patients undergoing primary MPFL reconstruction were identified. Small (3.2-mm), short, oblique tunnels were used for patellar fixation in 215 cases, and suture anchors were utilized in 169 cases. The small, oblique tunnels and suture anchor techniques both resulted in a low incidence of patellar fracture, with rates of 0.47% and 0%, respectively. The use of suture anchors was associated with an increased risk of subluxation or dislocation compared with small, oblique tunnels (odds ratio, 3.98; P = .028). No significant difference was found in the need for revision MPFL reconstruction surgery with suture anchors (odds ratio, 1.925; P = .66).

CONCLUSION

The use of small, oblique tunnels with hamstring autograft is a safe means of patellar fixation in MPFL reconstruction. The use of small, oblique tunnels for patellar fixation versus 2 suture anchors can result in material cost savings with no significantly increased risk for fracture as well as an overall reduction in complication rates.

The modified semi-tunnel bone bridge technique achieved statistically better knee function than the suture anchor technique

PURPOSE

The purpose of this study was to evaluate and compare the clinical outcomes of two different fixation techniques for anatomic medial patellofemoral ligament (MPFL) reconstruction.

METHODS

A retrospective study was undertaken between 2012 and 2018 of 60 cases of patellar dislocation who underwent surgical reconstruction between 2007 and 2010: 30 patients were treated with modified semi-tunnel bone bridge fixation (group A) and 30 patients with suture anchor fixation (group B). All patients had computed tomography scans available to review the patellar tilt angle and lateral patellar angle (LPA). In addition, a physical examination was performed, and the patellar apprehension sign and patellar stability were evaluated. Knee function was also evaluated using the Kujala score and Lysholm score.

RESULTS

At a minimum 5-year follow-up, the patellar tilt angle and LPA were restored to the normal range, and a significant difference was observed between the groups. There was a significant improvement in knee function in the Kujala and Lysholm scores after surgery in both groups. At the final follow-up, the mean Kujala and Lysholm scores in groups A and B were significantly different.

CONCLUSION

Both the semi-tunnel bone bridge and suture anchor fixation for double-bundle anatomic reconstruction of the MPFL can effectively restore patellar stability and improve knee function. The semi-tunnel bone bridge technique achieved statistically better knee function than the suture anchor technique at a minimum 5-year follow-up.

LEVEL OF EVIDENCE

III.

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.

Surgical Treatment for Congenital Dislocation of the Patella in a Young Adult: A Case Report

CASE

We present an 18-year-old man with poor alignment of the lower limbs, marked by congenital dislocation of the left patella, with gait impairment, and an associated 20° flexion contracture. Surgical treatment was performed with a single complex procedure with the release of the lateral retinaculum, capsule, and iliotibial tract, followed by a subtraction trochleoplasty, tibial tubercle transfer, elongation of the quadriceps tendon, and anatomical reconstruction of the medial patellofemoral ligament. At the 5-year follow-up, the patient had a significant improvement in gait pattern, with the patella centered on the new trochlear groove without any signs of patellar instability.

CONCLUSIONS

The approach of congenital dislocation of the patella is controversial, and although numerous procedures have been described in children, the approach in adults should be individually tailored. In this case, trochlear deepening and preserving the trochlear cartilage proved to be an effective option for treating a congenital dislocation.

Primary Medial Patellofemoral Ligament Repair Versus Reconstruction: Rates and Risk Factors for Instability Recurrence in a Young, Active Patient Population

PURPOSE

To comparatively evaluate the clinical outcomes and rates of recurrent instability in young patients with primary medial patellofemoral ligament (MPFL) repair or reconstruction, as well as to assess for radiologic risk factors for worse outcomes.

METHODS

A retrospective review identified all patients with lateral patellar instability who underwent either MPFL repair and/or imbrication or MPFL reconstruction without any additional osseous procedures between 2008 and 2015 at a single center. Demographic variables and preoperative magnetic resonance imaging were analyzed, and Kujala scores were obtained at a minimum 2-year follow-up. Risk factors for worse outcomes were assessed, including the Caton-Deschamps Index (CDI) Insall-Salvati Index, tibial tubercle-trochlear groove distance, and tibial tubercle-posterior cruciate ligament distance.

RESULTS

We identified 51 knees with isolated MPFL surgery (reconstruction in 32 and imbrication and/or repair in 19) at a mean of 59.7 months' follow-up (range, 24-121 months). The overall rate of recurrent dislocations was significantly greater in the repair group (36.9%) versus the reconstruction group (6.3%, P = .01), despite the average CDI being significantly higher in the reconstruction group (1.34 vs 1.23 in repair group, P = .04). No significant difference in the rate of return to baseline activity was found between the groups (77.8% in reconstruction group vs 70% in repair group, P = .62). The average Kujala score showed no significant difference between the repair and reconstruction groups (84.15 ± 14.2 vs 84.83 ± 14.38, P = .72). No imaging measurements were found to be predictive of a worse postoperative Kujala score; however, the average CDI among the MPFL repair failures (1.30 ± 0.05) was significantly higher than among the MPFL repair nonfailures (1.18 ± 0.12, P = .03).

CONCLUSIONS

MPFL reconstruction may provide improved midterm clinical outcomes and a decreased recurrence rate compared with MPFL repair. Increased patellar height as measured by the CDI may be a risk factor for recurrent patellar instability in patients who undergo isolated MPFL repair.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

No influence of patellar fixation technique on clinical outcomes of double-bundle medial patellofemoral ligament reconstruction: a systematic review

PURPOSE

To compare clinical outcomes of double-bundle medial patellofemoral ligament (MPFL) reconstruction with different patellar fixation techniques including Kujala score, functional failure and complications.

METHODS

Pubmed, Embase, and Cochrane Library databases were searched for studies with clinical results of double-bundle MPFL reconstruction. The hamstring tendon autografts were used, and femoral fixation was performed with bone tunnel and an interference screw, and knee fixation angle was less than or equal to 45°. Patellar fixation methods were broadly categorized into 3 treatment groups: suture anchor (SA), bone tunnel (BT) and suture techniques (SU). Pooled means for Kujala score and pooled estimates for functional failure rate and complication rate were compared.

RESULTS

21 studies (23 groups) consisting of 691 knees met the inclusion criteria. 12 groups with 344 knees were in SA group, 5 groups of 161 knees were in BT group and 6 groups with 186 knees were in SU group. Statistically significant differences in Kujala score were found among three groups, 90.2 (95% CI 88.7-91.7) in SA group, 88.7 (95% CI 85.3-92.2) in BT group and 89.4 (95% CI 84.2-94.6) in SU group (all P < 0.001), but these differences were not clinically significant. No statistically significant differences were found in the positive apprehension sign rate, recurrent subluxation or dislocation rate, and major or minor complication rate among three groups.

CONCLUSION

Patellar fixation with bone tunnel, suture anchor or suture techniques were all effective in the double-bundle MPFL reconstruction. The present systematic review failed to show that one technique was better than the others. More high-quality trials and randomized controlled trials are needed.

Application of the Chinese Aircraft-shaped Sleeve system in the treatment of tibial shaft fractures using a suprapatellar approach for tibial intramedullary nailing: a randomised controlled trial

Background

The use of the suprapatellar approach for intramedullary nailing has recently become popular for the treatment of tibial fractures. This study aimed to investigate the effectiveness of using the Chinese Aircraft-shaped Sleeve (CASS) system on the clinical outcomes of tibial intermedullary nailing using a suprapatellar approach for the treatment of tibial fractures in a cohort of adult Chinese patients.

Methods

Magnetic resonance images (MRI) of the knee joints of 212 healthy adults with normal lower limb function from May 2011 to May 2015 were obtained from a level I Chinese regional trauma centre. Sixty inpatients at the same trauma centre who underwent treatment for tibial shaft fractures from June 2015 to June 2018 were enrolled. Tibial intramedullary nailing fixation of tibial shaft fractures via the suprapatellar approach was performed with either a CASS system or a conventional sleeve. The measurements of patellofemoral joint anatomy, the surgical time, the assessments of the patellofemoral joint cartilage conditions, and information of residual debris based on arthroscopic analysis were subsequently collected.

Results

The mean patellar angle (PA), sulcus angle (SA), sulcus width (SW) and sulcus depth (SD) were 135.40 ± 6.20°, 142.37 ± 5.33°, 33.37 ± 2.73 mm, and 4.29 ± 0.63 mm, respectively. The surgical time until entry reaming commencement and the irrigation time were significantly lower in the CASS group (P < 0.001). The difference in cartilage damage rate between groups was statistically significant (P = 0.031); the difference in residual debris conditions was not statistically significant (P = 0.1967).

Conclusion

The use of the CASS system could improve clinical outcomes of intramedullary nailing via suprapatellar approach for patients with a small patellofemoral joint space.

Medial patellofemoral ligament repair restores stability in pediatric patients when compared to reconstruction

BACKGROUND

Pediatric patellar instability has a high recurrence rate with non-operative care, and medial patellofemoral ligament (MPFL) reconstruction has known complications. MPFL repair offers an alternative method to restore patellar stability. This study's purpose was to assess the outcomes of MPFL repair in a pediatric cohort, and to compare these outcomes to a cohort of pediatric patients who underwent MPFL reconstruction.

METHODS

One surgeon performed 16 MPFL repairs on pediatric patients for traumatic patellar instability, with an average follow-up of 1.5 years. Age, sex, skeletal maturity, trochlear dysplasia, additional procedures, final range of motion, and complications were recorded. A sub-cohort with >1 dislocation (10 patients) was compared to a historical group (22 patients) with >1 dislocation who underwent allograft MPFL reconstructions by the same surgeon.

RESULTS

Ten out of 16 (63%) patients had >1 dislocation event at time of presentation. Thirteen out of 16 (81%) patients had trochlear dysplasia. There were no complications and no recurrent instability in the repair group at last follow-up. Patients in the reconstruction group were older than the repair group (15.6 years vs. 13.0 years, p < 0.05), had lower Caton-Deschamps ratio (1.2 vs. 1.4, p < 0.05), and had lower percentage of additional procedures (59% vs. 100%, p < 0.05). There were three complications in the reconstruction group: two patients with recurrent instability and one patient with patella fracture requiring revision surgery.

CONCLUSIONS

MPFL repair in pediatric patients resulted in a low risk of recurrent instability with rates comparable or better than that of allograft reconstruction.

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 Using All-Soft Suture Anchors for Patellar Fixation

The medial patellofemoral ligament (MPFL), which is critical for both patellar stability and normal kinematics of the patellofemoral joint, is disrupted in most patellar dislocations. Consequently, MPFL reconstruction is advocated in recurrent dislocations to restore native patellar constraints. Fixation of the MPFL graft to the medial border of the patella can be achieved through various methods, each with its own benefits and drawbacks. We present a technique for MPFL fixation to the patella using all-soft suture anchors, theoretically decreasing the risk of patellar fracture and articular surface violation.

Evaluation of the Schöttle Technique in the Pediatric Knee

Background

The Schöttle point is commonly used for anatomic femoral tunnel placement during medial patellofemoral ligament (MPFL) reconstruction. This technique has not been previously validated in the skeletally immature patient, in whom femoral tunnel placement may put the distal femoral physis at risk of iatrogenic injury.

Hypothesis

Interobserver reliability for femoral tunnel placement will be higher in adult knees compared with pediatric knees.

Study Design

Cross-sectional study (diagnosis); Level of evidence, 3.

Methods

We selected 30 perfect lateral radiographs for this study: 20 from pediatric knees (mean patient age, 10 years; range, 8-11 years) and 10 from adult knees (mean patient age, 18.5 years; range, 18-23 years). Six observers with varying levels of clinical experience evaluated each radiograph and approximated the site of the MPFL femoral tunnel using the Schöttle technique. Intra- and interobserver reliabilities for femoral tunnel placement were evaluated. Statistical analysis was used to compare measurements.

Results

During initial interobserver measurements, the diameter of the composite perfect circles averaged 9.0 and 6.8 mm in adult and pediatric knees, respectively (P = .004). At repeat measurement, circles averaged 9.8 and 7.3 mm in adult and pediatric knees, respectively (P = .0001). Femoral tunnel placement intraobserver variance averaged 2.9 mm in adult knees (range, 1.9-4.0 mm) and 2.3 mm in pediatric knees (range, 1.9-2.9 mm). This difference was not significant (P = .14).

Conclusion

This study demonstrated that interobserver variance is actually greater in adult knees compared with pediatric knees, although interobserver variance was significantly different for both populations. Additionally, intraobserver variance is small on repeat measures, demonstrating that the Schöttle technique is reproducible for individual observers. Sources of this increased variance between observers are differences in agreement on the bony landmarks required for the Schöttle technique. Due to this variability in tunnel placement, we recommend caution when the Schöttle technique is used in pediatric knees to avoid iatrogenic injury to the distal femoral physis during femoral tunnel placement.

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.

Increased internal femoral torsion can be regarded as a risk factor for patellar instability - A biomechanical study

BACKGROUND

Increased internal femoral torsion is regarded as a risk factor for patellar instability. Biomechanical investigations confirming this hypothesis are missing.

METHODS

Eight fresh-frozen cadaver knees were tested on a specially designed simulator. Patellar motion and patellofemoral pressure were evaluated for 0°, 10°, and 20° of increased internal and external femoral torsion with native and with transected medial patellofemoral ligaments used to simulate patellar instability. A regression analysis was used for statistical analysis.

FINDINGS

In native medial patellofemoral ligaments, there were no significant changes in mean or peak pressures for any torsional states (P≥0.07). At 20° increased internal femoral torsion, there was a significant center of force shift towards the lateral side (P=0.01). Patellar shift was directed laterally at low knee flexion angles up to 30°. Lateral patellar tilt increased significantly at 10° and 20° of increased internal femoral torsion (P≤0.004). In transected medial patellofemoral ligaments, mean pressure (P≤0.005) and peak pressure (P≤0.02) decreased significantly for all torsional states. There was a significantly greater lateral center of force shift with increased internal femoral torsion (P≤0.04). Lateral patellar tilt increased significantly (P<0.001). Patellar shift did not change significantly with increased internal femoral torsion (P≥0.30).

INTERPRETATION

In a native medial patellofemoral ligament, 20° of increased internal femoral torsion can be regarded as a significant risk factor for patellar instability. With an insufficient medial patellofemoral ligament, 10° of increased internal femoral torsion already represents a significant risk factor.

Why Do Patellofemoral Stabilization Procedures Fail? Keys to Success

In recent years, surgical interventions for patellofemoral joint instability have gained popularity, possibly revitalized by the recent advances in our understanding of patellofemoral joint instability and the introduction of a number of new surgical procedures. This rise in surgical intervention has brought about various complications. In this review article, we present the complications that are associated with 5 main surgical procedures to stabilize the patella-medial patellofemoral ligament reconstruction, tibial tubercle osteotomy, trochleoplasty, lateral release/lateral retinacular lengthening, and derotation osteotomies. The key to success and potential problems with these surgical techniques are highlighted in the form of "expert takeaways."

The influence of medial patellofemoral ligament reconstruction on clinical results and sports activity level

OBJECTIVES

The aim of this study was to demonstrate postoperative outcomes and return to regular physical and sports activities at average of 6 years after patellar stabilization with medial patellofemoral ligament (MPFL) reconstruction.

METHODS

Between November 2006 and January 2010, 31 isolated MPFL reconstructions in 29 patients with recurrent patellar dislocation were performed. Radiographs and magnetic resonance imaging were evaluated preoperatively. Knee function was assessed pre- and postoperative using Kujala score and the patient satisfaction, according to the International Knee Documentation Committee (IKDC) score. Tegner activity score was used for the evaluation of sports activity level.

RESULTS

The average follow-up was 6.4±1.2 years. All measured scores increased significantly at follow-up. The average Kujala score increased from 75±10 to 95±10, patient satisfaction according to IKDC score from 6.1±1.4 to 8.7±1.4 and Tegner activity score from 4.4±1.6 to 5.7±1.3. The Tegner activity score after surgery was significantly lower than the score before the patellar dislocation (6.7±1.3). There were no significant differences in Kujala postoperative score between women's and men's group (P=0.25). There was no significant correlation between body mass index and Kujala score postoperatively (P=0.11) and between age at surgery and Kujala scores postoperatively (P=0.56). Patients who were active in sports preoperatively had resumed sports activities in 88.5% after surgery, 69.6% of them returned to the same levels and 30.4% return to the lower levels.

CONCLUSION

Patellar stabilization with MPFL reconstruction is a safe and effective treatment method for all patients with patellofemoral instability and allows most patients to return to regular physical and sports activities after surgical intervention. Although sports activity level increased significantly after surgery, the same level of sports activity before the patellar dislocation has not been achieved.

Evaluation of the isometry of different points of the patella and femur for medial patellofemoral ligament reconstruction

BACKGROUND

The location of patellar and femoral fixation of the graft in medial patellofemoral ligament reconstructions has been widely discussed. This study aimed to assess the distances between different patellar and femoral fixation points to identify the least anisometric pairs of points.

METHODS

Ten cadaver knees were attached to an apparatus that simulated an active range of motion of 120°, with three metallic markers fixed onto the medial side of the patella, and seven markings onto the medial epicondyle. The examined points included the proximal patella pole (1), the patellar center (3), the midpoint between points 1 and 3 (2), a point directly on the epicondyle (6), points 5mm anterior (5) and posterior (7) to the epicondyle, points 5mm anterior to point 5 (4) and 5mm posterior to point 7 (8), and points 5mm proximal (9) and distal (10) to the epicondyle. The distances between patella and femur points were measured by a photogrammetry system at 15° intervals.

FINDINGS

The pair of points that exhibited the lowest average variability in distance, and hence was the most isometric, was the patella center combined with the anterior to the medial femoral epicondyle. The pairs of points that exhibited the highest average variability in distance, and hence were the least isometric, were the ones located distal or posterior to the medial femoral epicondyle, with less influence by the patellar location.

INTERPRETATION

Surgeons should avoid positioning the graft distally or posterior to the epicondyle due to the increase in anisometry.

Reconstruction of the medial patellofemoral ligament by means of the anatomical double-bundle technique using metal anchors

Objective

To evaluate double-bundle reconstruction of the medial patellofemoral ligament (MPFL) using a graft from the semitendinosus tendon and fixation with metal anchors over the medium term.

Methods

This was a prospective cross-sectional study. After approval from the research ethics committee, 31 patients with patellofemoral instability who underwent MPFL reconstruction by means of the anatomical double-bundle technique, with fixation using metal anchors, were analyzed between May 2010 and January 2015. To evaluate the effectiveness of the MPFL reconstruction surgery, the Kujala scale and the Tegner–Lysholm score were assessed before the procedure and one year afterwards, along with clinical data such as pain levels, range of motion and J sign. The data were tabulated in the Excel^® software and were analyzed using the SPSS Statistics^® software, version 21. The statistical analysis was performed using the Wilcoxon T test and the McNemar test.

Results

The mean preoperative score from the Kujala test was 45.64 ± 1.24 and the postoperative score was 94.03 ± 0.79 (p < 0.001). The preoperative Tegner–Lysholm score was 40.51 ± 1.61 and the postoperative score was 91.64 ± 0.79 (p < 0.001). The preoperative range of motion was 125.96 ± 2.11 and the postoperative range was 138.38 ± 1.49 (p < 0.05).

Conclusion

MPFL reconstruction by means of the anatomical double-bundle technique is easily reproducible, without episodes of recurrence, with satisfactory results regarding restoration of stability and function of the patellofemoral joint.

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.

RANDOMIZED PROSPECTIVE STUDY ON TRAUMATIC PATELLAR DISLOCATION: CONSERVATIVE TREATMENT VERSUS RECONSTRUCTION OF THE MEDIAL PATELLOFEMORAL LIGAMENT USING THE PATELLAR TENDON, WITH A MINIMUM OF TWO YEARS OF FOLLOW-UP

Objective: The aim of this study was to compare the surgical results from reconstruction of the medial patellofemoral ligament (MPFL) with non-operative treatment of primary patellar dislocation. Methods: Thirty-nine patients (41 knees) with patellar dislocation were randomized into two groups. One group was treated conservatively (immobilization and physiotherapy) and other was treated surgically with reconstruction of the MPFL, and the results were evaluated with a minimum follow-up of two years. The Kujala questionnaire was applied to assess pain and quality of life, and recurrences were evaluated. Pearson's chi-square test and Fisher's exact test were used in the statistical evaluation. Results: The statistical analysis showed that the mean Kujala score was significantly lower in the conservative group (70.8), compared with the mean value in the surgical group (88.9), with p = 0.001. The surgical group presented a higher percentage of “good/excellent” Kujala score results (71.43%) than in the conservative group (25.0%), with p = 0.003. The conservative group presented a greater number of recurrences (35% of the cases), while in the surgical group there were no reports of recurrences and/or subluxation. Conclusions: Treatment with reconstruction of the medial patellofemoral ligament using the patellar tendon produced better results, based on the analysis of post-treatment recurrences and the better final results from the Kujala questionnaire after a minimum follow-up period of two years.

BIOMECHANICAL ACCESS METHOD FOR ANALYZING ISOMETRICITY IN RECONSTRUCTING THE MEDIAL PATELLOFEMORAL LIGAMENT

OBJECTIVE

To present a biomechanical device for evaluating medial patellofemoral ligament (MPFL) reconstruction and its isometricity.

METHODS

An accessible biomechanical method that allowed application of physiological and non-physiological forces to the knee using a mechanical arm and application of weights and counterweights was developed, so as to enable many different evaluations and have a very accurate measurement system for distances between different structures, for analysis on experiments. This article describes the assembly of this system, and suggests some practical applications. Six cadaver knees were studied. The knees were prepared in a testing machine developed at the Biomechanics Laboratory of IOT-HCFMUSP, which allowed dynamic evaluation of patellar behavior, with quantification of patellar lateralization between 0° and 120°. The differences between the distances found with and without load applied to the patella were grouped according to the graft fixation angle (0°, 30°, 60° or 90°) and knee position (intact, damaged or reconstructed).

RESULTS

There was a tendency for smaller lateral displacement to occur at fixation angles greater than 30 degrees of flexion, especially between the angles of 45° and 60° degrees of flexion, after the reconstruction. For the other angles, there was no statistical significance.

CONCLUSION

The method developed is a useful tool for studies on the patellofemoral joint and the MPFL, and has a very accurate measurement system for distances between different structures. It can be used in institutions with fewer resources available.

Clinical-radiographic correlation of the femoral insertion point of the graft in reconstruction of the medial patellofemoral ligament

OBJECTIVE

To analyze the radiographic positioning of the femoral tunnel and correlate this with the postoperative clinical results among patients undergoing reconstruction of the medial patellofemoral ligament (MPFL) alone.

METHOD

This was a retrospective study in which 30 knees of 26 patients with recurrent dislocation of the patella that underwent MPFL reconstruction were evaluated. The femoral insertion point of the graft and the postoperative clinical condition were analyzed and correlated using the Kujala and Lysholm scales.

RESULTS

22 knees presented a femoral tunnel in the anatomical area (group A) and 8 outside of this location (group B). In group A, the mean score on the Kujala scale was 89.68 points and on the Lysholm scale was 92.45 points. In group B, the mean score on the Kujala scale was 84.75 points and on the Lysholm scale was 92 points. The difference between the means was not significant on either of the two scales.

CONCLUSION

Correlation with the clinical results did not show any difference in relation to the positioning of the femoral insertion of the graft.

The double-pulley technique for anatomical double-bundled medial patellofemoral ligament reconstruction

INTRODUCTION

Majority of the current medial patellofemoral ligament (MPFL) reconstruction techniques vary with respect to methods of fixation on the patella. In an effort to maximise the area of patellar footprint coverage and minimise the complication of patellar fracture, we developed a procedure that implemented the double-pulley suture anchors technique.

DESIGN

Prospective case series.

SETTING

A primary medical centre in Kaohsiung, Taiwan.

PATIENTS AND METHODS

Eighteen consecutive patients (18 knees) who met the inclusion criteria underwent the aforementioned operation between January 2010 and March 2012. Patients were evaluated using functional scores (Kujala and Tegner-Lysholm scores), apprehension test, and radiographic examination (congruence angle and patellar tilting angle) preoperatively and at the follow-up.

RESULTS

The mean follow-up was 35 months. A firm endpoint to lateral patellar translation was noted in all patients at the last follow-up with a mean lateral translation quadrant of 1.5 (improved from 3.5 preoperatively, p<0.001). Both clinical and radiographic assessment improved significantly (p<0.001); the mean Kujala score improved from 55.3±6.8 preoperatively to 95.2±3.5 at the last follow-up; TegnerLysholm from 43.6±8.1 to 93.6±6.8; the mean congruence angle improved from 20.6°±2.1° preoperatively to -5.2°±2.4° at the last follow-up; and the patellar tilting angle from 23.8°±2.3° to 9.6°±1.3°.

CONCLUSION

The double-pulley patellar fixation technique, by having a result that is comparable with those of other studies that used aperture fixation techniques, can be a promising surgical option for anatomically reconstructing the medial petellofemoral ligament.

Length change behavior of virtual medial patellofemoral ligament fibers during in vivo knee flexion

BACKGROUND

In vivo length change behavior of native medial patellofemoral ligament (MPFL) fibers throughout the range of knee motion has not been reported in vivo.

PURPOSE

To measure the length changes of various fibers of the MPFL and to determine their length change patterns during in vivo passive knee flexion.

STUDY DESIGN

Descriptive laboratory study.

METHODS

The right knees of 11 living subjects were scanned with a high-resolution computed tomography scanner at 0°, 30°, 60°, 90°, and 120° of knee flexion, and 3-dimensional (3D) models were constructed using customized software. Five patellar points were determined: 20% (point 20), 30% (point 30), 40% (point 40), 50% (point 50), and 60% (point 60) from the superior pole of the patella. The Schöttle femoral point (point F) was marked on a translucent 3D model of a true lateral view. Five virtual fibers connecting these points on the 3D knee model were created, and the lengths of various fibers were digitally measured.

RESULTS

The average length changes were 9.1±2.5 mm in F20, 9.1±2.5 mm in F30, 8.1±2.6 mm in F40, 6.9±2.4 mm in F50, and 6.9±1.7 mm in F60. There were significant differences in length changes of these 5 fibers (P<.001). The lengths of 2 superior fibers (F20 and F30) increased as the knee flexed from 0° to 30° and decreased as the knee flexed over 30°. The lengths of a middle fiber (F40) and an inferior fiber (F50) increased from 0° to 30°, reached a plateau from 30° to 60°, and then decreased from 60° to 120°. F60 showed an increase from 0° to 30°, and then a plateau pattern from 30° to 90°, followed by a decrease during further flexion.

CONCLUSION

Superior fibers exhibited their maximum lengths at low flexion angles, and inferior fibers exhibited their maximum lengths at midflexion angles. The MPFL is a complex of functionally various fibers with some taut and others slack over the whole range of knee motion.

CLINICAL RELEVANCE

The results for lengths and length change patterns of various MPFL fibers are expected to serve as a theoretical background for anatomic double-bundle MPFL reconstruction.

MPFL reconstruction: technique and results

Patellar instability is a common problem, and medial patellofemoral ligament (MPFL) injury is inherent with traumatic patellar dislocations. Initial nonoperative management is focused on reconditioning and strengthening the dynamic stabilizers of the patella. For those patients who progress to recurrent instability, further investigation into the predisposing factors is required. MPFL reconstruction is indicated in patients with recurrent instability and insufficient medial restraint due to MPFL injury. A technique of MPFL reconstruction is outlined. This procedure may also be performed in combination with other realignment procedures.

MPFL reconstruction using a quadriceps tendon graft: part 2: operative technique and short term clinical results

BACKGROUND

We describe the preliminary clinical results of a new operative technique for MPFL reconstruction using a strip of quadriceps tendon (QT).

PATIENTS

17 patients (7 male, 10 female; mean age 21.5 years ± 3.9) have been operated on with this technique. All patients were evaluated clinically, radiologically and with subjective questionnaires (Tegner-, Lysholm-, Kujala Score) pre-operatively and post-operatively at 6 and 12 months (m).

SURGICAL TECHNIQUE

A 10 to 12 mm wide, 3mm thick and 8 to 10 cm long strip from the central aspect of quadriceps tendon is harvested subcutaneously. The tendon strip is then dissected distally on the patella, left attached, diverged 90° medially underneath the medial prepatellar tissue and fixed with 2 sutures. The graft is fixed in 20° of knee flexion with a bioabsorbable interference screw.

RESULTS

Lysholm score at 6m was 81.9 ± 11.7 and at 12 m 88.1 ± 10.9, Kujala score at 12 m was 89.2 ± 7.1 and Tegner Score was 4.9 ± 2.0 (6m) and 5.0 ± 1.9 (12 m). Two patients had a positive apprehension test at 12 months. There was no re-dislocation during the follow-up period.

CONCLUSION

MPFL reconstruction with a strip of QT harvested in a minimal invasive technique was found to be associated with good short term clinical results. We think that this technique presents a valuable alternative to common hamstring techniques for primary MPFL reconstruction in children and adults, as well as for MPFL revision surgery.

LEVEL OF EVIDENCE

IV, prospective case series.

The relationship of the femoral physis and the medial patellofemoral ligament in children: a cadaveric study

BACKGROUND

Patellar dislocations are common in skeletally immature athletes, and the medial patellofemoral ligament (MPFL) is an important primary restraint to lateral patellar translation. The relationship between the MPFL femoral origin footprint and femoral physis is unclear. The purpose of this study was to evaluate the MPFL femoral origin footprint and its relationship to the femoral physis in skeletally immature anatomic specimens.

METHODS

Six skeletally immature cadaver knee specimens were examined through gross dissection (group A: 1, 11, and 11 mo; and group B: 8, 10, and 11 y). Metallic markers were placed at the center of the MPFL femoral origin footprint. Computed tomography scans for each specimen were analyzed. The MPFL footprint width, and the vertical distances from the center and proximal extent of the MPFL footprint to the medial aspect of the physis were measured.

RESULTS

The mean width of the MPFL femoral origin footprint was 0.70 cm (0.48 to 1.09 cm) and 1.12 cm (1.03 to 1.29 cm) for groups A and B, respectively. The mean distance from the center of the MPFL origin footprint to medial aspect of the distal femoral physis was 0.90 cm (0.52 to 1.30 cm) and 0.40 cm (0.00 to 0.86 cm) distal to the physis for groups A and B, respectively. The mean distance from the proximal extent of the MPFL origin footprint to the medial aspect of the femoral physis was -0.55 cm (-0.28 to -1.03 cm) and 0.16 cm (-0.34 to 0.64 cm) for groups A and B, respectively.

CONCLUSIONS

All subjects were found to have a center of the MPFL origin footprint at or below the physis. The proximal extent of the MPFL origin footprint was found to extend above the physis in the 2 older specimens.

CLINICAL RELEVANCE

The relationship of the MPFL origin footprint to the femoral physis in the skeletally immature is not well understood. These dissections may be useful to surgeons performing MPFL reconstructions in skeletally immature patients.

Patellofemoral chondral status after medial patellofemoral ligament reconstruction using second-look arthroscopy in patients with recurrent patellar dislocation

BACKGROUND

Most patients with recurrent patellar dislocation show cartilage damage in the patellofemoral joint. Medial patellofemoral ligament reconstruction has become one of the most important surgical techniques for treating recurrent patellar dislocation. However, patellofemoral chondral status after this reconstruction has not been elucidated. The purpose of this study was to investigate the effects of medial patellofemoral ligament reconstruction on articular cartilage in the patellofemoral joint by comparing the arthroscopic chondral status at the time of reconstruction with that at second-look arthroscopy.

METHODS

Participants in the present study comprised 31 patients (22 females, 9 males; 32 knees) who underwent second-look arthroscopy at a median of 12 months (range 6-40 months) after dual tunnel medial patellofemoral ligament reconstruction using a double-looped autologous semitendinosus tendon graft. Median age at the time of initial surgery was 20 years (range 13-43 years). The patellofemoral joint was divided into six portions, comprising the medial facet of the patella, central ridge, lateral facet of the patella, anterior medial femoral condyle, femoral groove, and anterior lateral femoral condyle. Chondral status in each portion according to the International Cartilage Repair Society classification was retrospectively evaluated at the time of initial surgery and second-look arthroscopy.

RESULTS

Before medial patellofemoral ligament reconstruction, chondral lesions were observed in the patellofemoral joint in 31 knees (97%). At the central ridge of the patella, chondral damage was observed in 22 knees (69%) at initial surgery and damaged cartilages showed recovery in 6 knees. No significant difference in the alteration of chondral status was seen for the medial facet, lateral facet of the patella, anterior medial femoral condyle, femoral groove, and anterior lateral femoral condyle.

CONCLUSIONS

According to short-term results, the patellofemoral chondral status after medial patellofemoral ligament reconstruction was not altered at second-look arthroscopy in most part of patellofemoral joint. At the central ridge of the patella, significant improvement of the International Cartilage Repair Society grading was observed.

Anatomic medial patellofemoral ligament reconstruction using patellar suture anchor fixation for recurrent patellar instability

PURPOSE

The purpose of this study was to prospectively evaluate clinical and radiographic outcomes following anatomic medial patellofemoral ligament (MPFL) reconstruction using patellar suture anchor fixation for recurrent patellar instability.

METHODS

Twenty patients (20 knees) were enrolled in this study. The median age was 21 years, and the median follow-up was 34.5 months. Reconstruction was performed using a hamstring autograft fixed with two suture anchors at native patellar site of the MPFL. No patient had undergone additional medial tibial tuberosity transfer. Clinical scores (Kujala, Lysholm, and Tegner score) and apprehension test were completed preoperatively and at the follow-up. Preoperative and follow-up radiographic assessments included modified Insall-Salvati ratio, congruence angle, and lateral patellofemoral angle.

RESULTS

The preoperative Kujala and Lysholm scores were 52.6±12.4 and 49.2±10.7, and at follow-up visits, corresponding values were 90.9±4.5 (p<0.001) and 90.9±5.2 (p<0.001). Tegner score increased from 3.0 (range 1-4) to 5.0 (range 4-7) (p<0.001). The apprehension test was positive in all patients preoperatively, but only positive in one patient at follow-up. All radiographic assessments were significantly improved; modified Insall-Salvati index (from 1.75 to 1.65) (p=0.002), congruence angle (from 6.3° to -7.0°) (p<0.001), and lateral patellofemoral angle (from 2.1° to 4.9°) (p=0.008). No patient experienced a patellar fracture or redislocation.

CONCLUSION

These results are comparable to those of bone tunnel techniques reported in the literature. This study shows that anatomic MPFL reconstruction using two suture anchors is a reliable treatment option.

LEVEL OF EVIDENCE

Case series with no comparison group, Level IV.

Variations in kinematics and function following patellar stabilization including tibial tuberosity realignment

PURPOSE

The current study was performed to characterize the influence of patellar stabilization procedures on patellofemoral and tibiofemoral dynamic motion.

METHODS

Six knees were evaluated pre-operatively and 1 year or longer following stabilization via tibial tuberosity realignment, with simultaneous medial patellofemoral ligament reconstruction performed for five knees. Knees were imaged during extension against gravity using a dynamic CT scanner. Models representing each knee at several positions of extension were reconstructed from the images. Local coordinate systems were created within one femur, patella and tibia for each knee, with shape matching of the bones used to transfer the coordinate axes to the other models. The patellar lateral shift and tilt and tibial external rotation were quantified based on the reference axes and interpolated to flexion angles from 5° to 40°. Pre-operative and post-operative data were compared with the paired t tests.

RESULTS

Surgical realignment significantly decreased the average patellar lateral shift and tilt at low flexion angles. At 5°, surgical realignment decreased the average lateral shift from 15.5 (6.3) to 8.5 (4.7) mm and decreased the average lateral tilt from 20.8 (9.4)° to 13.8 (6.4)°. The changes were statistically significant (p<0.05) at 5° and 10° of flexion, as well as 20° for lateral shift. The average tibial external rotation also increased significantly at 30° and 40° following surgery.

CONCLUSION

Patellar stabilization including a component of tuberosity realignment reduces patellar lateral shift and tilt at low flexion angles, but the long-term influence of increased tibial external rotation on tibiofemoral function is currently unknown.

LEVEL OF EVIDENCE

Prospective comparative study, Level II.

Reliability of radiographic landmarks in medial patello-femoral ligament reconstruction in relation to the anatomical femoral torsion

PURPOSE

Anatomically correct graft positioning at the femoral insertion site is a key factor in surgical reconstruction of the medial patello-femoral ligament (MPFL). Basically there are two techniques to define this point in fluoroscopy during surgery. The role of the anatomical femoral torsion on the accuracy and reproducibility of both procedures has not been clarified.

METHODS

Twenty human anatomical leg specimens were dissected. The femoral insertion of the MPFL was marked by two K-wires. The position of the ligament insertion was determined fluoroscopically in the true lateral view as used in routine clinical practice. The anatomical MPFL insertion was compared to the radiographic landmarks which were recommended by two previous studies. The anatomical femoral torsion of the specimens was assessed by computed tomography scans.

RESULTS

In true lateral view fluoroscopy, the mean distance of the femoral MPFL insertion was -0.2 mm distal to the vertical reference line intersecting the posterior point of Blumensaat's line. In the anteroposterior direction, the mean distance was -2.0 mm posterior to the femoral cortex reference line. There was no correlation between anatomical femoral torsion and the distance of the femoral MPFL insertion to the posterior cortex.

CONCLUSIONS

The results of this study strongly recommend use of a vertical line intersecting the most posterior point of Blumensaat's line as a reference to identify the MPFL insertion in the craniocaudal direction. In the anteroposterior direction, the femoral MPFL insertion showed distinctive variation and was found -2.0 mm posterior to the femoral cortex reference line without being influenced by the anatomical femoral torsion.

Use of contact pressure-sensitive surfaces as an indicator of graft tension in medial patellofemoral ligament reconstruction

BACKGROUND

No previous description has been made about an objective method to test the graft resistance in MPFL reconstruction intraoperatively. In our study, we aimed to obtain intraoperative objective data about the graft resistance using contact pressure-sensitive surfaces and measuring pressure formed under the graft.

MATERIALS AND METHODS

In 2012, double-layered contact pressure-sensitive Fuji Prescale Film bands were placed under MPFL in 15 fresh-frozen high above-knee amputates (Group 1) and under graft in 10 patients who underwent MPFL reconstruction (Group 2). Measured values at different flexion angles were compared between and in groups.

RESULTS

Statistical analysis was performed by Student's t test. It has been found that the pressure under the graft was higher in patients having reconstruction as compared to the pressure under natural MPFL. Decreasing pressure values were observed with increasing flexion angles in both groups.

CONCLUSION

Contact pressure-sensitive surfaces provided objective data when placed under the graft in natural MPFL and during surgery. Therefore, they may be used as an objective marker providing information about graft resistance.

Sectioning the medial patellofemoral ligament alters patellofemoral joint kinematics and contact mechanics

Medial patellofemoral ligament (MPFL) disruption may alter patellofemoral joint (PFJ) kinematics and contact mechanics, potentially causing pain and joint degeneration. In this controlled laboratory study, we investigated the hypothesis that MPFL transection would change patellar tracking and PFJ contact pressures and increase the distance between the attachment points of the MPFL. Eight fresh frozen dissected cadaveric knees were mounted in a rig with the quadriceps and ITB loaded to 205 N. An optical tracking system measured joint kinematics, and pressure sensitive film between the patella and trochlea measured PFJ contact pressures. Length patterns of the distance between the femoral and patellar attachments of the MPFL were measured using a suture led to a linear displacement transducer. Measurements were repeated with the MPFL intact and following MPFL transection. A significant increase in the distance between the patellar and femoral MPFL attachment points was noted following transection (p < 0.05). MPFL transection resulted in significantly increased lateral translation and lateral tilt of the patella in early flexion (p < 0.05). Peak and mean medial PFJ contact pressures were significantly reduced and peak lateral contact pressures significantly elevated in early knee flexion following MPFL transection (p < 0.05). MPFL transection resulted in significant alterations to PFJ tracking and contact pressures, which may affect articular cartilage health.

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

PURPOSE

Retinacular restraints have a critical role in patellar tracking, limiting the movement of the patella in the trochlear groove. The medial patellofemoral ligament (MPFL) is probably the main stabilizer against lateral displacement; few studies are focused on MPFL role on patellofemoral kinematics and patellar stability. The main goal of this in vitro study was to analyse the influence of the MPFL on the kinematics of the patellofemoral joint and patellar stability.

METHODS

Using a non-image-based navigation system, kinematics and anatomical data of six fresh-frozen specimens were collected. A passive flexion-extension from 0° to 90° and static acquisitions at 0°, 30°, 60° and 90°, with and without 25 N of lateral load, were performed with intact and resected MPFL with a 60 N axial force applied to the isolated quadriceps tendon. Patellar tilt and shift were analysed.

RESULTS

The MPFL intact state showed a shift in medial direction during the first degrees of knee flexion-that disappeared in MPFL resected condition-followed by a lateral shift, similar to that of MPFL resected condition. Tilt analysis showed that patella rotated laterally until 85° of knee flexion for intact MPFL condition and until 70° for resected MPFL condition and after rotated medially. Static tests showed that patellar stability was significantly affected by MPFL resected condition in particular at 30° and 60°.

CONCLUSIONS

The MPFL has an aponeurotic nature. It works as a restraint during motion, with an active role under high stress on lateral side, but with a small contribution during neutral knee flexion. Its biomechanical behaviour under loading conditions should be kept into account when performing surgical reconstruction of this ligamentous structure.

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.

The influence of risk factors on clinical outcomes following anatomical medial patellofemoral ligament (MPFL) reconstruction using the gracilis tendon

PURPOSE

Patellofemoral instability is influenced by ligamentous, boney and neuromuscular factors. The most important variables are trochlea geometry, medial patellofemoral ligament (MPFL), patella height, tibial tuberosity-trochlea groove distance (TT-TG) and the extensor muscles. Treatment is complicated by these multifactorial conditions. This prospective study examined the influence of risk factors on clinical results and athletic activities where treatment was confined to ligamentous procedures only.

METHODS

Fifty patients with chronic patellofemoral instability were treated with MPFL reconstruction using an autologous gracilis tendon. Clinical data, radiographs and magnetic resonance imaging (MRI) were prospectively evaluated pre- and postoperative (minimum follow-up 12 month) to detect existing risk factors for patellofemoral instability and to evaluate clinical and sport ability scores (Kujala, Valderrabano).

RESULTS

There was a low rate of redislocation (2 %) and an average Kujala score of 87 ± 13 points postoperative. The MRI showed good integration of the reconstructed MPFL and a positive effect regarding the decrease of patella tilt (16.1° to 11.2°). A negative relationship was found between the degree of trochlear dysplasia and outcomes. 80 % of all patients returned to the same or higher level of physical activity.

CONCLUSIONS

Addressing only ligamentous factors through MPFL reconstruction leads to satisfying clinical results and low redislocation rates in most patients. In cases with a high degree of trochlear dysplasia and enlarged TT-TG, additional procedures such as trochleaplasty and tibial tuberosity transfer should be considered as well.

LEVEL OF EVIDENCE

IV.

Medial patellofemoral ligament reconstruction - A novel technique

Patellofemoral instability is initially treated conservatively and surgical treatment is reserved for resistant cases. Reconstruction of medial patellofemoral ligament has gained popularity these days as it attempts at restoring soft tissue anatomy and biomechanics of medial patellar restraint back to normal. Here we describe our novel transverse patella single tunnel and femoral interference screw technique to reconstruct the medial patellofemoral ligament using free autologous gracilis and semitendinosus grafts.

Incidence and radiologic predictor of postoperative patellar instability after Fulkerson procedure of the tibial tuberosity for recurrent patellar dislocation

PURPOSE

Excellent results of anteromedialization of the tibial tuberosity for recurrent patellar dislocation have been reported; however, the contribution of the preoperative anatomic factors to postoperative patellar instability has not been well established. The purpose of this study was to investigate the mid-term results and the incidence of postoperative patellar instability after Fulkerson procedure for recurrent patella dislocation, and to determine the radiologic predictor of the postoperative patellar instability.

METHODS

Sixty-two knees of 41 patients underwent Fulkerson procedure with or without lateral retinacular release for recurrent patellar dislocation and were followed-up for 85-155 months. Predisposing anatomic factors for recurrent patellar dislocation were evaluated preoperatively, including valgus knee alignment (femorotibial angle), patella alta (Insall-Salvati ratio), trochlear dysplasia (trochlear depth), lateral patellar displacement (congruence angle) and lateral malposition of the tibial tuberosity (tibial tuberosity-trochlear groove distance). The relationship between the measurements of anatomic factors and postoperative patellar instability, which was defined by the patellar re-dislocation or residual apprehension after surgery, was analyzed.

RESULTS

The Fulkerson score and the Kujala score were significantly improved from the median of 65 (35-80) points and 68 (36-82) points preoperatively to 95 (60-100) points and 92 (57-100) points at the final follow-up, respectively. Three knees (4.8%) experienced postoperative patellar re-dislocation and 4 knees (6.5%) showed the positive apprehension sign at the final follow-up. The statistical analysis showed that the postoperative patellar instability correlated with only patella alta.

CONCLUSION

Patella alta was the only predictor of postoperative patellar instability after Fulkerson procedure. These results indicated that isolated Fulkerson procedure should not be indicated for recurrent patellar dislocation with severe patella alta.

LEVEL OF EVIDENCE

Case-control study, Level III.

In-vivo patellar tendon kinematics during weight-bearing deep knee flexion

This study quantified in-vivo 3D patellar tendon kinematics during weight-bearing deep knee bend beyond 150°. Each knee was MRI scanned to create 3D bony models of the patella, tibia, femur, and the attachment sites of the patellar tendon on the distal patella and the tibial tubercle. Each attachment site was divided into lateral, central, and medial thirds. The subjects were then imaged using a dual fluoroscopic image system while performing a deep knee bend. The knee positions were determined using the bony models and the fluoroscopic images. The patellar tendon kinematics was analyzed using the relative positions of its patellar and tibial attachment sites. The relative elongations of all three portions of the patellar tendon increased similarly up to 60°. Beyond 60°, the relative elongation of the medial portion of the patellar tendon decreased as the knee flexed from 60° to 150° while those of the lateral and central portions showed continuous increases from 120° to 150°. At 150°, the relative elongation of the medial portion was significantly lower than that of the central portion. In four of seven knees, the patellar tendon impinged on the tibial bony surface at 120° and 150° of knee flexion. These data may provide useful insight into the intrinsic patellar tendon biomechanics during a weight-bearing deep knee bend and could provide biomechanical guidelines for future development of total knee arthroplasties that are intended to restore normal knee function.

Changes in the length of the medial patellofemoral ligament: an in vivo analysis using 3-dimensional computed tomography

BACKGROUND

The ideal points for medial patellofemoral ligament (MPFL) reconstruction have not been precisely defined.

PURPOSE

To determine at which flexion angles the grafts should be fixed to best restore patellar stability as well as to compare the length change of various femoral and patellar fixation sites for current MPFL reconstruction during knee flexion in vivo.

STUDY DESIGN

Descriptive laboratory study.

METHODS

The right knees of 10 living patients were scanned with a high-resolution computed tomography scanner at 0°, 30°, 60°, 90°, and 120° of knee flexion, and 3-dimensional knee models were constructed using customized software. Based on recent anatomic studies and current surgical techniques, 4 femoral points (A: adductor tubercle; B: midpoint between the medial epicondyle and the adductor tubercle; C: medial epicondyle; and D: 10 mm inferior to the adductor tubercle) and 2 patellar points (30% [point 1] and 45% [point 2] from the proximal pole of the patella) were marked. The lengths of the 8 ligaments were digitally measured, and the length changes of these ligaments at the 5 different knee flexion angles were calculated.

RESULTS

Two ligaments including the adductor tubercle (A1, A2) showed an increase while the knee was flexed over 60°. Four ligaments (B1, B2, D1, D2) showed a slight increase as the knee flexed from 0° to 30° and a decrease as the flexion angle exceeded 30°. Length changes in these 6 ligaments were not significantly different. There was no significant difference between 2 patellar points in the length changes of these 6 ligaments. Two ligaments including the medial epicondyle (C1, C2) showed an excessive decrease during knee flexion and showed greatest length changes.

CONCLUSION

The femoral fixation sites should be located at point B or point D. Point A and point C are not ideal femoral fixation sites. The best angle for graft fixation would be near 30° of knee flexion.

CLINICAL RELEVANCE

The data obtained for length and length change pattern in each virtual ligament will serve as a useful basis for improved MPFL reconstruction.