Robert N. Steensen

The Anatomy and Isometry of the Medial Patellofemoral Ligament Implications for Reconstruction

Background Several techniques have been described for reconstruction of the medial patellofemoral ligament. However, the isometry of the medial patellofemoral ligament has not been studied. Purpose To define the anatomy and isometry of the medial patellofemoral ligament. Study Type Cadaveric study. Methods The authors dissected the medial patellofemoral ligament in 11 cadaveric knees and recorded its anatomic relationships. They evaluated the isometry of the medial patellofemoral ligament by obtaining measurements between various anatomic pairings at certain fixed angles of knee flexion. Results During knee flexion from 0° to 90°, the portion of the medial patellofemoral ligament from the inferior patellar attachment to the superior femoral attachment was nearly isometric, demonstrating an average change in length of only 1.1 mm. Statistical analysis showed the superior femoral attachment to be most significant in determining isometric behavior. Conclusions The most isometric portion of the medial patellofemoral ligament is the inferior portion of its patellar attachment extending to the superior portion of its femoral attachment, with the superior femoral attachment having the most notable influences on isometry. Clinical Relevance This study provides a detailed description of the anatomy of the medial patellofemoral ligament, as well as an evaluation of the isometric behavior of the ligament. Application of these data during reconstruction of the medial patellofemoral ligament may help to optimize patellofemoral stability.BACKGROUND Several techniques have been described for reconstruction of the medial patellofemoral ligament. However, the isometry of the medial patellofemoral ligament has not been studied. PURPOSE To define the anatomy and isometry of the medial patellofemoral ligament. STUDY TYPE Cadaveric study. METHODS The authors dissected the medial patellofemoral ligament in 11 cadaveric knees and recorded its anatomic relationships. They evaluated the isometry of the medial patellofemoral ligament by obtaining measurements between various anatomic pairings at certain fixed angles of knee flexion. RESULTS During knee flexion from 0 degrees to 90 degrees, the portion of the medial patellofemoral ligament from the inferior patellar attachment to the superior femoral attachment was nearly isometric, demonstrating an average change in length of only 1.1 mm. Statistical analysis showed the superior femoral attachment to be most significant in determining isometric behavior. CONCLUSIONS The most isometric portion of the medial patellofemoral ligament is the inferior portion of its patellar attachment extending to the superior portion of its femoral attachment, with the superior femoral attachment having the most notable influences on isometry. CLINICAL RELEVANCE This study provides a detailed description of the anatomy of the medial patellofemoral ligament, as well as an evaluation of the isometric behavior of the ligament. Application of these data during reconstruction of the medial patellofemoral ligament may help to optimize patellofemoral stability.

The Prevalence and Combined Prevalences of Anatomic Factors Associated With Recurrent Patellar Dislocation A Magnetic Resonance Imaging Study

Background: Anatomic factors, including patella alta, increased tibial tubercle–trochlear groove (TT-TG) distance, rotational deformities, and trochlear dysplasia, are associated with dislocation of the patella. Identifying the presence of these anatomic factors both in isolation and in combination may influence treatment in patients with patellar dislocation. Purpose: The aim of this study was to compare the prevalence and combined prevalences of these anatomic factors using magnetic resonance imaging in a group of patients with and without histories of recurrent dislocation of the patella. Study Design: Case-control study; Level of evidence, 3. Methods: The prevalence and combined prevalences of patella alta, increased TT-TG distance, rotational deformity, and trochlear dysplasia on magnetic resonance imaging were reported and compared in 60 patients (60 knees) with and 120 patients (120 knees) without histories of recurrent patellar dislocation. Results: Patients with recurrent patellar dislocation possessed higher rates of patella alta (60.0% vs 20.8%), increased TT-TG distance (42.0% vs 3.2%), rotational deformity (26.7% vs 2.5%), and trochlear dysplasia (68.3% vs 5.8%) compared with patients without histories of patellar dislocation. Multiple anatomic factors were identified in 58.3% of patients (35/60) with recurrent dislocation compared with only 1.7% of controls (2/120). Conclusion: Recurrent patellar dislocation is associated with an increased prevalence of patella alta, increased TT-TG distance, rotational deformity, and trochlear dysplasia compared with patients with no histories of patellar dislocation. Multiple anatomic factors were identified in the majority of patients with recurrent dislocation. Further research may identify which factors play a greater role in patellar stability and may allow physicians to predict which first-time dislocation patients are more likely to sustain recurrence.

Reconstruction of the medial patellofemoral ligament using a quadriceps tendon graft: a case series.

UNLABELLED This study assessed medial patellofemoral ligament reconstruction using a partial-thickness quadriceps tendon graft in 14 knees in 13 patients. Nine patients were available for follow-up after a minimum of 24 months. Final patient evaluation was performed an average of 42 months postoperatively (range, 28-65 months). Primary outcome measure was occurrence of patellar dislocation postoperatively, and outcomes were quantified using the Kujala questionnaire and Crosby and Insall criteria. Postoperatively, no patient reported patellar dislocation. Using Crosby and Insall criteria, good or excellent results were achieved in 100% of patients. Mean Kujala score was 91.9. Postoperatively, all patients reported their knee was improved. These findings indicate medial patellofemoral ligament reconstruction with a quadriceps tendon graft is effective in preventing patellar dislocation and improving quality of life. However, patients should be counseled this procedure is indicated primarily for the treatment of recurrent instability, and postoperative relief of anterior knee pain is inconsistent. LEVEL OF EVIDENCE Level IV, Case Series.

Computational analysis of factors contributing to patellar dislocation.

Treatment for an initial incidence of patellar dislocation is usually conservative management; however, almost half of patients experience a subsequent, or multiple, dislocation(s). Patients often undergo multiple procedures which fail to treat the underlying anatomic abnormalities. The objective of this study was to evaluate interactions between key predisposing anatomic factors to patellar dislocation and identify combinations of abnormal factors which increase the risk of recurrent lateral dislocation. Four factors associated with lateral patellar dislocation were identified (sulcus angle, Insall‐Salvati ratio, tibial tubercle‐trochlear groove distance, and femoral anteversion). A finite element model of the patellofemoral joint was developed and parameterized so that a value for each factor could be applied and the model geometry/alignment would be modified accordingly. 100 combinations of the four factors were generated in separate computational simulations and resulting kinematics and forces of the patellofemoral joint were recorded. Sulcus angle was the most impactful factor on constraint. Multiple abnormal factors were generally required to produce the extremes of patellar alignment observed in this analysis. Understanding the underlying anatomic factors, and their effect on joint mechanics, for patients with recurrent lateral patellar dislocation will aid in determining optimal treatment pathways on a patient‐specific basis.

The medial patellofemoral ligament.

There has been substantial progress in our understanding of the medial patellofemoral ligament during the past 10 years. This structure is the primary static soft-tissue restraint to lateral patellar displacement. Substantial alteration of normal patellar tracking occurs after sectioning of the ligament. Clinical studies have demonstrated the medial patellofemoral ligament is disrupted during acute patellar dislocation. Recently, several medial patellofemoral ligament-based procedures have been developed for the treatment of patellar instability with good early results. However, further studies are needed to define the exact role of these procedures in the treatment of patellofemoral instability.

A comparison of autogenous patellar tendon and hamstring tendon grafts for anterior cruciate ligament reconstruction

Several graft options exist for reconstruction of the deficient ACL. The most commonly used grafts are the BPTB and quadrupled hamstring tendon autografts. Based on a comprehensive review of the literature, one graft is not superior to the other. Advantages and disadvantages are associated with the use of each graft. Surgeons who perform ACL reconstruction should be familiar with the use of both grafts.

Perioperative morbidity and mortality of 2-team simultaneous bilateral total knee arthroplasty.

Total knee arthroplasty (TKA) has a well-established track record for relieving pain associated with arthritis of the knee joint. The total rate of bilateral TKA has doubled over the past 2 decades, and the rate in women has tripled over that same time period. In patients with bilateral knee arthritis, a decision must be made whether to operate at 2 different settings (staged), a single setting with 1 surgeon (sequential simultaneous), or a single setting with 2 surgeons (2-team simultaneous). The purpose of this study was to examine the perioperative morbidity and mortality of 2-team simultaneous bilateral TKA. Two hundred twenty-seven consecutive 2-team simultaneous bilateral TKA and 216 consecutive unilateral TKA patients were reviewed. Major (deep infection, death, cerebrovascular accident, myocardial infarction, pulmonary embolism, revision within the 1-year follow-up) and minor (all other) complications were compared. No deaths occurred, and the major and minor complication rates were not statistically significantly different between the 2 groups, but a trend toward higher rates of both major and minor complications existed in the bilateral TKA group. Two-team simultaneous bilateral TKA offers the potential benefits of decreased overall recovery time, decreased overall cost, decreased number of anesthetic administrations, and simultaneous correction of significant deformity. It remains an appropriate option in select patients.

Perioperative safety of two-team simultaneous bilateral total knee arthroplasty in the obese patient

BackgroundAlthough the rates of perioperative morbidity and mortality with simultaneous bilateral total knee arthroplasty remain a concern, multiple studies have shown the procedure to be safe in selected patient populations. Evidence also remains mixed regarding the outcomes of total knee arthroplasty in obese patients. The purpose of this paper is to compare the rates of perioperative morbidity and mortality in consecutive obese patients undergoing two-team simultaneous bilateral total knee arthroplasty and unilateral total knee arthroplasty.MethodsThe records on all two-team simultaneous total knee arthroplasties and unilateral total knee arthroplasties from October 1997 to December 2007 were reviewed. A total of 151 patients with a body mass index (BMI) >30 undergoing two-team simultaneous total knee arthroplasty and 148 patients with a BMI >30 undergoing unilateral total knee arthroplasty were retrospectively reviewed and analyzed to determine perioperative morbidity and mortality as well as one-year mortality rates.ResultsPreoperative patient characteristics did not show any significant differences between groups. The simultaneous bilateral group had significantly longer operative times (127.4 versus 112.7 minutes, p < 0.01), estimated blood loss (176.7 versus 111.6 mL, p = 0.01), percentage of patients requiring blood transfusion (64.9% versus 13.9%, p < 0.01), length of hospital stay (3.72 versus 3.30 days, p < 0.01), and percentage of patients requiring extended care facility usage at discharge (63.6% versus 27.8%, p < 0.01). No significant difference between unilateral and bilateral groups was seen in regards to total complication rate, major or minor complication subgroup rate, or any particular complication noted. Doubling the variables in the unilateral group for a staged total knee arthroplasty scenario did create significant increases over the simultaneous data in almost every data category.ConclusionsTwo-team simultaneous total knee arthroplasty appears to be safe in obese patients, with similar complication rates as compared to unilateral procedures. Two-team simultaneous total knee arthroplasty also appears to have potential benefits over a staged procedure in the obese patient, although more study is required regarding this topic.

The Effect of Intercondylar Notchplasty on the Patellofemoral Articulation

Using pressure-sensitive film, we measured the patel lofemoral contact areas and pressures after increasing degrees of notchplasty in eight fresh-frozen cadaveric knee specimens. Each specimen was stabilized on an axial loading frame with physiologic loads applied through the quadriceps tendon at varying flexion an gles. The patellofemoral joint was loaded at 90°, 105°, and 120° of knee flexion. The same measurements were then obtained after serial notchplasties of 3, 6, and 9 mm. The film was analyzed for contact areas and for contact pressures by densitometry. There was no statistical significance between contact area or pres sure after notchplasties of 3, 6, or 9 mm at 90°, 105°, and 120° of knee flexion. These data suggest that routine notchplasty does not affect the patellofemoral articulation.

Excursion of oscillating saw blades in total knee arthroplasty.

Intraoperative disruption of the medial collateral ligament during total knee arthroplasty is an uncommon complication that can be avoided by retractor placement as well as by careful cutting of the femur and tibia. This study evaluated the excursion of a small and large oscillating saw blade and compared the data against the widths of both the medial and lateral femoral condyle cuts. We discovered that the large saw blade had a statistically significantly larger excursion than the medial and lateral condyle width in women, as well as the lateral condyle width in men. The small saw blade excursion did not exceed any condyle width. We conclude that the smaller saw blade should be considered when making these cuts because the excursion of the large saw blade may exceed the width of cut needed and endanger important structures such as collateral ligaments.