The Anatomy of the Extensor Mechanism

Can the Surgical Approach to Total Knee Arthroplasty Influence Early Postoperative Outcomes? - A Comparative Study between Trivector and Medial Parapatellar Approaches

Background:

Trivector approach to total knee arthroplasty (TKA) is a quadriceps tendon sparing approach, whereas the medial parapatellar (MPP) approach involves making a longitudinal incision in quadriceps tendon. We postulated that quadriceps-sparing approach such as trivector should make postoperative rehabilitation easier and ultimately reduce the length of hospital stay.

Objectives:

The aim of the study is to compare the early postoperative outcomes of the TKA performed through the trivector and the MPP approaches.

Methodology:

We prospectively reviewed the results of 56 consecutive patients operated on by two knee surgeons: one routinely performs trivector and the other an MPP approach. Both the groups consisted of 28 patients each. We looked at operative times, the time taken to perform straight leg raise (SLR), range of movements achieved before discharge, and length of the hospital stay.

Results:

The mean time taken for performing the surgery through the MPP approach was 56 min, whereas, for the trivector approach, it was 54 min (P = 0.31). The mean time taken to perform SLR in the MPP approach group was 3.5 days, whereas in the trivector group, the meantime taken for SLR was 2.5 days (P = 0.003). The average extension at the time of discharge in the MPP group was 3.8°, and in the trivector group, it was 0.86° (P = 0.007). The average knee flexion at the time of discharge in the MPP group was 84.2°, whereas in the trivector group, it was 86.5° (P = 0.199). The average hospital stay in the MPP group was 5.96 days, whereas in the trivector group, it was 4.84 days (P = 0.11).

Conclusions:

The trivector approach patients took significantly less time to do SLR and achieved a better range of extension before discharge from the hospital. The patients with trivector approach were discharged early by one day, although it is not statistically significant, it is clinically significant.

Recognition of evolving medial patellofemoral anatomy provides insight for reconstruction

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

V.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

V.

Quantitative and Qualitative Analysis of the Medial Patellar Ligaments: An Anatomic and Radiographic Study

BACKGROUND

The qualitative and quantitative anatomy of the medial patellar stabilizers has been reported; however, a quantitative analysis of the anatomic and radiographic attachments of all 4 ligaments relative to anatomic and osseous landmarks, as well as to one another, has yet to be performed.

PURPOSE

To perform a qualitative and quantitative anatomic and radiographic evaluation of the medial patellofemoral ligament (MPFL), medial patellotibial ligament (MPTL), medial patellomeniscal ligament (MPML), and medial quadriceps tendon femoral ligament (MQTFL) attachment sites, with attention to their relationship to pertinent osseous and soft tissue landmarks.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Ten nonpaired fresh-frozen human cadaveric knees were dissected, and the MPFL, MPTL, MPML, and MQTFL were identified. A coordinate measuring device quantified the attachment areas of each structure and its relationship to pertinent bony landmarks. Radiographic analysis was performed through ligament attachment sites and relevant anatomic structures to assess their locations relative to pertinent bony landmarks.

RESULTS

Four separate medial patellar ligaments were identified in all specimens. The center of the MPFL attachments was 14.3 mm proximal and 2.1 mm posterior to the medial epicondyle and 8.3 mm distal and 2.7 mm anterior to the adductor tubercle on the femur and 8.9 mm distal and 19.9 mm medial to the superior pole on the patella. The MQTFL had a mean insertion length of 29.3 mm on the medial aspect of the distal quadriceps tendon. The MPTL and MPML shared a common patellar insertion and were 9.1 mm proximal and 15.4 mm medial to the inferior pole. The MPTL attachment inserted on a newly identified bony ridge, which was located 5.0 mm distal to the joint line. The orientation angles of the MPTL and MPML with respect to the patellar tendon were 8.3° and 22.7°, respectively.

CONCLUSION

The most important findings of this study were the correlative anatomy of 4 distinct medial patellar ligaments (MPFL, MPTL, MPML, MQTFL), as well as the identification of a bony ridge on the medial proximal tibia that consistently served as the attachment site for the MPTL. The quantitative and radiographic measurements, while comparable with current literature, detailed the meniscal insertion of the MPML and defined a patellar insertion of the MPTL and the MPML as a single attachment. The data allow for reproducible landmarks to be established from previously known bony and soft tissue structures.

CLINICAL RELEVANCE

The findings of this study provide the anatomic foundation needed for an improved understanding of the role of medial-sided patellar restraints. This will help to further refine injury patterns and/or soft tissue deficiencies that result in lateral patellar instability, which can then be addressed with an anatomic-based reconstruction or repair technique and potentially lead to improved outcomes.

Cadaveric study of the secondary medial patellar restraints: patellotibial and patellomeniscal ligaments

PURPOSE

To detail the anatomy of the medial patella stabilizers, medial patellotibial (MPTL), and medial patellomeniscal ligaments (MPML), focusing on the points of origin and insertion, length, thickness, width, and fibres orientation to study the frequency of anatomical variations and the anatomy of these ligaments, thereby improving surgical techniques.

METHODS

Thirty dissected knees were analysed. A digital caliper was used to measure the length, thickness, and width, as well as the mid-point of the ligaments insertion and the distance from the MPTL insertion to the articular surface of the tibia. The angle of inclination of the ligaments was calculated in the coronal plane. The collected data were tabulated and statistically analysed.

RESULTS

MPTL was present in 90 % as a visible thickening of the deep medial retinaculum and exhibiting only one anatomical variation. The MPML was absent in one of the dissected knees, and one anatomical variation was found. The tilt angle of the ligaments was very similar, with an average of 22.2° ± 7.6° for the MPTL and 24.2° ± 6.6° for the MPML.

CONCLUSION

The MPTL is a long visible structure of the deep layer of the medial retinaculum, but with a distinct origin and insertion. The MPML is thicker with an angular direction similar to MPTL. The presence of these ligaments in most of the specimens studied suggests that the real anatomical and biomechanical importance of these ligaments should be further investigated because they play a role in the patellar stability.

Using Electromyography to Detect the Weightings of the Local Muscle Factors to the Increase of Perceived Exertion During Stepping Exercise

Rate of perceived exertion (RPE) is a clinically convenient indicator for monitoring exercise intensity in cardiopulmonary rehabilitation. It might not be sensitive enough for clinicians to determine the patients' physiological status because its association with the cardiovascular system and local muscle factors is unknown. This study used the electromyographic sensor to detect the local muscle fatigue and stabilization of patella, and analyzed the relationship between various local muscle and cardiovascular factors and the increase of RPE during stepping exercise, a common exercise program provided in cardiopulmonary rehabilitation. Ten healthy adults (4 males and 6 females) participated in this study. Each subject used their right bare foot to step up onto a 23-cm-high step at a constant speed until the RPE score reached 20. The RPE, heart rate (HR), and surface EMG of the rectus femoris (RF), vastus medialis, and vastus lateralis were recorded at 1-minute intervals during the stepping exercise. The generalized estimating equations (GEE) analysis indicated that the increase in RPE significantly correlated with the increase in HR, and decrease in median frequency (MF) of the EMG power spectrum of the RF. Experimental results suggest that the increase in RPE during stepping exercise was influenced by the cardiovascular status, localized muscle fatigue in the lower extremities. The weighting of the local muscle factors was more than half of the weighting of the cardiovascular factor.

Intraosseous blood flow of the everted or laterally-retracted patella during total knee arthroplasty

Patellofemoral problems are relatively common sequelae of total knee arthroplasty (TKA), and many factors contribute to these complications. Vascular compromise has been identified as a possible contributing factor, and was selected for further investigation in the present study. Laser Doppler Flowmetry was used to quantify patella intraosseous blood flow in vivo during TKA surgery without the use of a tourniquet. Flow was measured after medial parapatellar arthrotomy, and compared to flow during patella eversion and lateral retraction. Patella blood flow during eversion was reduced to 13% of baseline values (p<0.05). A significantly greater proportion of flow was preserved during lateral retraction (53%), although the reduction from baseline was still significant (p<0.05). A statistically significant difference in flow (60% of baseline) was also noted when the leg was flexed from full extension to 90 degrees (p<0.05) with the patella in its normal anatomical alignment. In this study, we have demonstrated the sensitivity of the patella blood supply to knee flexion angle and patella dislocation technique, particularly to patella eversion. These may be important findings with regard to surgical technique for TKA.

Assessment and management of chronic patellofemoral instability

Chronic patellofemoral instability can be a disabling condition. Management of patients with this condition has improved owing to our increased knowledge of the functional anatomy of the patellofemoral joint. Accurate assessment of the underlying pathology in the unstable joint enables the formulation of appropriate treatment. The surgical technique employed in patients for whom non-operative management has failed should address the diagnosed abnormality. We have reviewed the literature on the stabilising features of the patellofemoral joint, the recommended investigations and the appropriate forms of treatment.

Structural parameters of the vastus medialis muscle and its relationship to patellofemoral joint deterioration

Vastus medialis (VM) muscle dysfunction and abnormal limb alignment are commonly observed in patients who experience changes in patellofemoral joint (PFJ) function, leading many clinicians to assume that there is a direct relationship between VM structural parameters, leg alignment, and PFJ dysfunction. This study tested the hypothesis that there is a relationship between structural parameters of the VM muscle, limb alignment, and the location and severity of patellofemoral joint deterioration (PFJD). The dissection study used 32 limbs from 24 intact cadavers. Data were collected on limb alignment, angle of VM muscle fibers below the superior aspect of the patella, length of VM inserting on the medial aspect of the patella, and severity and location of PFJD. Parametric and nonparametric statistical analyses illustrated that PFJD was most commonly located on the middle third of the medial half of the patellar articular surface. The severity of PFJD did not vary with location. There was no significant correlation between any of VM insertion length, VM fiber angle, limb alignment, and PFJD location and severity lpar;r(2) < 0.34). The results of this study did not support the hypothesis of a relationship between structural parameters of the VM muscle, limb alignment, and the location and severity of PFJD in this subject group. Future research should examine the relationship between functional parameters of the entire quadriceps muscle group and PFJ dysfunction.

Patella intraosseous blood flow disturbance during a medial or lateral arthrotomy in total knee arthroplasty: a laser Doppler flowmetry study

Patella complications are recognized sequelae of total knee arthroplasty (TKA). Disruption of blood flow to the patella and adjacent soft tissues during surgery may contribute to reduced viability of the bone and patella ligament tissue. The effect on genicular blood flow to the medial and lateral patella was compared for a medial (MA) and lateral arthrotomy (LA) during TKA. Laser Doppler flowmetry was used to measure both baseline and postarthrotomy flow in vivo for 16 primary TKA patients. Flow in the lateral patella was reduced approximately 20% for both MA and LA. Conversely, the use of MA resulted in substantial reduction in flow to the medial patella (53%) compared to the lateral approach (27%). A large standard deviation of scores was evident in all cases. Although there was a tendency for LA to disturb the patellar blood flow less, the difference was not significant. It was concluded that neither approach is superior regarding the blood flow preservation to the patella. Hence, a lateral approach might only have an advantage in knee joints that are likely to need a lateral release in combination with an MA-e.g., a valgus deformity or preoperative patella maltracking.

The extensor mechanism of the knee joint: an anatomical study

This study investigated the anatomy of the structures that form the extensor mechanism of the knee joint using microsurgical techniques. Ten fresh-frozen human adult cadaveric knees were used. The quadriceps components, the infrapatellar tendon, the patellofemoral ligaments, and their relations to the neighboring anatomical structures were measured. The angles of the vastus lateralis and the vastus medialis muscle fibers to the rectus tendon were 26.6 and 41.1 degrees , respectively. The medial patellofemoral ligament connecting the femoral medial epicondyle to the medial edge of the patella was approximately 54.2 mm long, and its width ranged from 9 to 30 mm. The medial patellomeniscal ligament had a wide attachment to the meniscus whereas the attachment to the patella was narrow. The patellar tendon was 31.9 mm broad at its attachment to the apex of the patella and 27.4 mm wide at its attachment to the tibial tubercle. It was 38-49 mm long. Using the surgical microscope we were able to dissect and identify a trilaminar arrangement of prepatellar fibrous soft tissues. Also, we were able to identify the vessels and nerves around the patella. Details of clinical relevance and the possible pathological implications of the material presented are discussed. Emphasis is placed on the stability of the patellofemoral joint and the complex interaction between a range of factors providing it.

In vivo and noninvasive three-dimensional patellar tracking induced by individual heads of quadriceps

PURPOSE

Unbalanced actions of the quadriceps components are closely linked to patellar mal-tracking and patellofemoral pain syndrome. However, it is not clear how individual quadriceps components pull and rotate the patella three dimensionally. The purpose of this study was to investigate in vivo and noninvasively patellar tracking induced by individual quadriceps components.

METHODS

Individual quadriceps component was activated selectively through electrical stimulation at the muscle motor point, and the resulting patellar tracking was measured in vivo and noninvasively in 18 knees of 12 subjects. The in vivo and noninvasively patellar tracking was corroborated with in vivo fluoroscopy and in vitro cadaver measurements.

RESULTS

Vastus medialis (VM) mainly pulled the patella first in the medial and second in the proximal directions and vastus lateralis (VL) pulled first in the proximal and second in the lateral directions. The oblique portion (VMO) of the VM pulled the patella mainly medially and the longus portion (VML) more proximally. Medial tilt was the major patellar rotation induced by VMO contraction at full knee extension. With the knee at the more flexed positions, the amplitude of patellar movement induced by comparable quadriceps contractions was reduced significantly compared to that at full knee extension, and VMO changed its main action from extending to flexing the patella.

CONCLUSIONS

The medial and lateral quadriceps components moved the patella in rather different directions, and rotated the patella differently about the mediolateral tilt and mediolateral rotation axes but similarly in extension. The approach can be used to investigate patellar tracking in vivo and noninvasively in both healthy subjects and patients with patellofemoral disorder and patellar malalignment.

One-stage reconstruction of large midline abdominal wall defects using a composite free anterolateral thigh flap with vascularized fascia lata

OBJECTIVE

Large midline abdominal wall defects are continuously a challenge for reconstructive surgeons. Adequate skin coverage and fascia repair of the abdominal wall is necessary for achieving acceptable results. The purpose of this paper is to present a new approach to abdominal wall reconstruction using a free vascularized composite anterolateral thigh (ALT) flap with fascia lata.

METHODS

Seven patients with large full-thickness abdominal wall defects were successfully reconstructed by means of a composite ALT flap combined with vascularized fascia lata. The size of the skin islands ranged from 20 to 32 cm in length and 10 to 22 cm in width, and the vascularized fascia lata sheath measured 14 to 28 cm and 8 to 18 cm, respectively. Functional outcome of the abdominal wall strength and donor thigh morbidity were investigated by using a Cybex kinetic dynamometer.

RESULTS

All flaps survived. No postoperative ventral hernia occurred except for one mild inguinal incision hernia. Subjectively there were no significant donor site problems. Objective assessment was performed in 4 patients 2 years postoperatively. In the reconstructed abdomen, isokinetic concentric and eccentric measurements of extension/flexion ratios of the abdominal wall strength showed no apparent decrease compared with other references. Functional evaluation of quadriceps femoris muscle contraction forces after free ALT composite flap harvest showed an averaged deficit of 30% as compared with the contralateral legs. However, no difficulties in daily ambulating were reported by the patients.

CONCLUSION

The free composite ALT myocutaneous flap with vascularized fascia lata provides an alternative option for a stable repair in complex abdominal wall defects.

Soft-tissue anatomy anterior to the human patella

BACKGROUND

The purpose of this anatomic study is to report the results of dissections of the soft-tissue structures anterior to the human patella.

METHODS

Sixty-one fresh or fresh-frozen and thawed human cadaver knees were dissected for this study. Thirty-five of the knees were from men, and twenty-six were from women. The soft-tissue structures anterior to the patella were dissected layer by layer and documented photographically.

RESULTS

Fifty-seven (93%) of the sixty-one knees were found to have a trilaminar arrangement of fibrous soft-tissue structures anterior to the patella from superficial to deep. Those structures included a transversely oriented fascia, an obliquely oriented aponeurosis, and the longitudinally oriented fibers of the rectus femoris tendon. Between the soft-tissue fibrous layers, there were three prepatellar spaces that can be termed bursae: a prepatellar subcutaneous bursa, a prepatellar subfascial bursa, and a prepatellar subaponeurotic bursa. Four of the sixty-one knees lacked an intermediate oblique aponeurotic layer. In none of the sixty-one knees was there a potential bursal space between the rectus femoris tendon and the anterior patellar bone.

CONCLUSIONS

These anatomic findings are at variance with descriptions in standard anatomic orthopaedic texts and periodical literature, including the Nomina Anatomica. None of those texts accurately describe the presence of a prepatellar aponeurotic layer or a prepatellar subaponeurotic bursa. Also, in contradistinction to descriptions in the anatomic literature, including the Nomina Anatomica, no prepatellar subtendinous bursa was found in any of the sixty-one knees.

One-stage reconstruction of soft tissue and Achilles tendon defects using a composite free anterolateral thigh flap with vascularized fascia lata: clinical experience and functional assessment

The combined loss of the Achilles tendon with overlying soft tissue is a reconstructive challenge. To achieve acceptable rehabilitation, such patients need skin coverage including functional repair of the Achilles tendon. This article presents four such patients who were treated successfully by means of an anterolateral thigh (ALT) composite flap with vascularized fascia lata. The size of the ALT flaps ranged from 10 to 16 cm in length and 6 to 9 cm in width. All flaps included vascularized fascia lata, which was rolled to serve as vascularized tendon graft (range 8 x 6 cm to 10 x 8 cm) for reconstruction of the Achilles tendon defect. Flap success rate was 100%. All patients could walk and climb stairs without support; however, mild difficulty when running was reported. Functional outcome of the recipient ankle and donor thigh morbidity were investigated by using a kinetic dynamometer comparing reconstructed sides with the healthy contralateral limbs. This assessment was performed in two patients at 2 years postoperatively. In the reconstructed ankles, isokinetic concentric measurements of dorsiflexion and plantar flexion showed a deficit of 30% and 40%, respectively. Functional evaluation of quadriceps femoris muscle contraction forces after free ALT composite flap harvest showed a 10% to 25% deficit. However, there were no difficulties in daily ambulating. In summary, the free composite ALT flap with vascularized fascia lata provides an alternative option for Achilles tendon reconstruction in complex defects.

Techniques of medial retinacular repair and reconstruction

Insufficiency of the passive patellar restraints results in lateral patellar instability by allowing excessive lateral displacement of the patella. Although the surgical approach to patellar instability traditionally has been to realign the dynamic elements (muscle forces) that pull the patella laterally, newer techniques have sought to restore the integrity of key medial passive (ligamentous) stabilizers. An increasing body of evidence indicates that the chief medial ligamentous restraint is the medial patellofemoral ligament. The current authors examine the principles of medial retinacular repair and reconstruction as they relate to patellar stability. Individual techniques and approaches are discussed, including primary repair with or without augmentation, and reconstruction using autogenous tendon, allografts, and synthetic graft materials. These procedures share the common objective of addressing the essential lesion in lateral patellar instability to restore the normal passive restraints against lateral patellar displacement.

Outcome measurement in the treatment of extensor mechanism difficulties of the knee

The authors' underlying philosophy is to use a standardized data package to collect information prospectively. This allows for the clinical evaluation and research of extensor mechanism disabilities. The use of a system of data management allows meaningful follow-up comparisons. Thus, one patient at a time, a surgeon's experience is documented.

Activation of the VMO and VL during dynamic mini-squat exercises with and without isometric hip adduction

OBJECTIVE

the purpose of this study was to compare vastus medialis obliquus (VMO) and vastus lateralis (VL) activity while performing a mini-squat with and without isometric hip adduction.

DESIGN AND SETTING

a repeated measures within subjects design was used. Subjects performed two sets of three repetitions of a traditional mini-squat and a mini-squat with concurrent hip adduction (squeeze).

SUBJECTS

20 recreationally active subjects (10 men, 10 women age=28.10+/-5.91 years, height=170.94+/-11.03 cm, mass=72.32+/-16.66 kg) with no history of patellofemoral pain (PFP), quadriceps injury, or other knee injury participated in the study.

MEASUREMENTS

the EMG signal of the VMO and VL was recorded bilaterally during both exercises. EMG data were normalized to the maximal voluntary isometric contraction (MVIC) of the quadriceps produced during seated, isometric knee extension.

RESULTS

results of repeated measures ANOVA's revealed that the squeeze squat produced significantly greater VMO and VL activity than the traditional squat (p=0.02). For both the traditional and squeeze squats, intrasession reliability from the first to the second set was calculated using intraclass correlation coefficient (ICC) formula (3:1) bilaterally for both the VMO and the VL. All ICC values were greater than 0.9.

CONCLUSION

combining isometric hip adduction with a mini-squat exercise significantly increases the activity of the quadriceps. Performing mini-squats with isometric hip adduction will be beneficial to patellofemoral patients as they increase quadriceps activity, however, based on our data we cannot conclude that this exercise preferentially recruits the VMO. Further research is needed to determine the exact mechanism by which quadriceps function is altered.

Medial patellofemoral ligament injury following acute transient dislocation of the patella: MR findings with surgical correlation in 14 patients

PURPOSE

The purpose of this study was to determine the accuracy of MRI in determining both the extent and the location of injury to the medial patellofemoral ligament (MPFL).

METHOD

MR findings were compared to the surgical results of 14 consecutive patients who experienced transient patellar dislocation. Two musculoskeletal radiologists, blinded to the surgical results, retrospectively reviewed the MR studies, and a consensus reading was obtained.

RESULTS

Surgery demonstrated complete disruption of the MPFL in 7 of 14 patients (50%), with stretching or partial tearing of the MPFL in the remaining 7 (50%) patients. MRI was 85% sensitive and 70% accurate in detecting MPFL disruption. Vastus medialis obliquus muscle elevation was present in 12 of 14 (85%).

CONCLUSION

MRI accurately depicts both the extent and the location of MPFL injury following transient patellar dislocation and can therefore play a significant role in directing surgical management of these patients.

A comparison of the proximal and distal parts of the vastus medialis muscle

The vastus medialis muscle has two distinct parts with different fibre orientations and specific functions: the vastus medialis longus (VML) and the vastus medialis oblique/obliquus (VMO). A fascial plane dividing the two parts, and separate nerve branches supplying each muscle part have been reported. This study was designed to verify this. In 50 cadavers, the angular orientations of the VML and VMO fibres with the femoral axis were measured and found to be significantly different (t(49)=36.35; p<0.001). The VML and VMO were both shown to be innervated by femoral nerve branches. A fascial plane between the VML and VMO was demonstrated in one specimen only. In conclusion, the VML and VMO make up the vastus medialis muscle, a single muscle.

Free anterolateral thigh flap for extremity reconstruction: clinical experience and functional assessment of donor site

From August of 1995 through July of 1998, 38 free anterolateral thigh flaps were transferred to reconstruct soft-tissue defects. The overall success rate was 97 percent. Among 38 anterolateral thigh flaps, four were elevated as cutaneous flaps based on the septocutaneous perforators. The other 34 were harvested as myocutaneous flaps including a cuff of vastus lateralis muscle (15 to 40 cm3), either because of bulk requirements (33 cases) or because of the absence of a septocutaneous perforator (one case). However, vastus lateralis muscle is the largest compartment of the quadriceps, which is the prime extensor of the knee. Losing a portion of the vastus lateralis muscle may affect knee stability. Objective functional assessments of the donor sites were performed at least 6 months postoperatively in 20 patients who had a cuff of vastus lateralis muscle incorporated as part of the myocutaneous flap; assessments were made using a kinetic communicator machine. The isometric power test of the ratios of quadriceps muscle at 30 and 60 degrees of flexion between donor and normal thighs revealed no significant difference (p > 0.05). The isokinetic peak torque ratio of the quadriceps and hamstring muscles, including concentric and eccentric contraction tests, showed no significant difference (p > 0.05), except the concentric contraction test of the quadriceps muscle, which revealed mild weakness of the donor thigh (p < 0.05). In summary, the functional impairment of the donor thighs was minimal after free anterolateral thigh myocutaneous flap transfer.

The medial patellofemoral ligament revisited: an anatomical study

The purpose of this study was to provide a comprehensive description of the anatomy of the medial patellofemoral ligament (MPFL). The anterior and medial aspects of 4 unpreserved and 16 preserved cadaveric human knees were dissected with particular attention being paid to the relationship of the various layers to one another and to the place of the MPFL within these layers. We confirmed that the MPFL is a distinct structure lying within layer II. Its bulk varies considerably between individuals but not from side to side in a given individual. The visualisation, attachments, and gross morphology of the ligament are described. The attachments of the MPFL and the orientation of its fibres suggest that it may have a role in limiting lateral excursion of the patella. The common attachment of the tendon of the vastus medialis muscle and the ligament to the superomedial patella suggests that there may be a dynamic element to such a stabilising function.

The influence of weakness in the vastus medialis oblique muscle on the patellofemoral joint: an in vitro biomechanical study

OBJECTIVE

Investigation of the influence of weakness in the vastus medialis oblique muscle on patellar tracking.

DESIGN

In vitro biomechanical study.

BACKGROUND

Currently, the influence of weakness in the vastus medialis oblique muscle on patellar tracking has not been well understood.

METHODS

Seven human cadaveric knees were used. The direction of loading forces in the rectus femoris/vastus intermedius, vastus medialis oblique, and the vastus lateralis muscles was decided by the muscle alignment of each cadaver knee measured at the time of dissection. The loads used were 60 N in the rectus femoris, 50 N in the vastus lateralis, and 40 N in the vastus medialis oblique, according to the ratio calculated from the cross-sectional study. The weakness of vastus medialis oblique was simulated at 30 N (75%), 20 N (50%), 10 N (25%), and 0 N (0%), and the patellar position was measured for each condition using a magnetic 3 Space Tracker System. The influence of weakness in the vastus medialis oblique muscle on patellar position was investigated with seven cadaver knees using a magnetic 3 Space Tracker System.

RESULTS

At 0 degrees and 15 degrees of knee flexion, 75%, 50%, 25% and 0% of the normal vastus medialis oblique muscle led to a significant difference in lateral patellar shift compared to the normal (P<0.05).

CONCLUSIONS

Weakness of the vastus medialis caused the patellar lateral shift at 0 degrees and 15 degrees of knee flexion.

RELEVANCE

Weakness of the vastus medialis is thought to be an important factor causing patellar subluxation and dislocation. Understanding the relationship between the vastus medialis weakness and patellar tracking will be useful in diagnosis, treatment and prevention of patellar subluxation and dislocation.

The quadriceps angle: a review of the literature

Previous investigations of the quadriceps (Q) angle and its relationship to knee disorders have yielded equivocal results. The purpose of this paper is to present a review of the current literature on the Q angle and to examine the differences in Q angles when measured: 1) under differing measurement protocols; 2) between asymptomatic and symptomatic populations; 3) between male and female samples; and 4) from side to side within subjects. Little scientific evidence exists to support the commonly held assumptions that Q angles are larger in symptomatic vs. asymptomatic or that they are equal in the right vs. left lower limb. However, larger mean values are consistently observed in groups of young adult females vs. young adult males.

Medial soft tissue restraints in lateral patellar instability and repair

This study was undertaken to evaluate the medial ligamentous stabilizers of the patella in restraining lateral displacement and to assess their relative contribution after individual repair. Seventeen fresh frozen human anatomic specimen knee joints were studied. The specimens were loaded onto a testing instrument that was designed to measure the compliance of the medial and lateral patellar restraints in the coronal plane. Two different cutting and repair sequences were used to test the individual contributions of the patellar ligaments. The medial patellofemoral ligament was found to be the major medial ligamentous stabilizer of the patella. Isolated release resulted in a 50% increase in lateral displacement, and isolated repair restored balance to the patella. In addition, the patellotibial and patellomeniscal ligament complex played an important secondary role in restraining lateral patellar displacement. Isolated repair of these ligaments restored balance to near normal levels. The medial patellofemoral retinaculum played only a minor role in patellofemoral instability. Proximal realignment or medial ligament repair for patellofemoral instability specifically should address repair of the deep layers that contain the restraints to lateral patellar displacement. Failure to include these structures in repair, especially of the medial patellofemoral ligament, may lead to persistent or recurrent instability.

Soft tissue restraints to lateral patellar translation in the human knee

The purpose of this investigation was to identify and quantify the soft tissue restraints, both medially and laterally, to lateral patellar translation. These restraints to lateral patellar translation at 20 degrees of knee flexion were tested biomechanically on a universal testing instrument in nine fresh-frozen cadaveric knees. After preconditioning the tissues, the patella of each intact knee was translated laterally to a distance at which a force of 200 N was recorded. This distance was used to translate the patella for the remaining structures to be sectioned. The contribution of each structure to the total restraining force was determined as the percent of the force to restrain the intact specimen by sectioning the restraints in a predetermined order. The contribution of each structure to the restraining force was defined as the difference between the restraining force before and after its sectioning. The medial patellofemoral ligament was found to be the primary restraint to lateral patellar translation at 20 degrees of flexion, contributing 60% of the total restraining force. The medial patellomeniscal ligament contributed 13% of the total force, and the lateral retinaculum contributed 10%. The medial patellotibial ligament and superficial fibers of the medial retinaculum were not functionally important in preventing lateral translation. The previously unrecognized contribution of the lateral retinaculum as a restraint to lateral patellar translation may shed new light on the failures of isolated lateral release for acute lateral dislocation of the patella.

Reliability of the clinical assessment in predicting the cause of internal derangements of the knee

The reliability of the clinical assessment, which comprised history, physical examination, and plain radiographs, was determined by comparing the initial preoperative diagnosis with the postoperative diagnosis as determined arthroscopically, and by comparing the results of the clinical evaluation with published reports of arthrography, computed tomography (CT), and magnetic resonance imaging (MRI). The study group included 206 patients (216 knees) scheduled for arthroscopic surgery for suspected internal derangements. The primary preoperative clinical diagnosis was correct in 175 knees (81%), with an overall accuracy of 93%, sensitivity of 89%, and specificity of 94%. The most common preoperative diagnoses were medial and lateral meniscal tears. Results of the clinical assessment were comparable or superior to published reports of arthrography, CT, and MRI. Thus, it may be unnecessary to routinely use these costly special studies to determine the need for arthroscopic surgery. We conclude that a thorough clinical assessment can provide sufficient information for the surgeon to make a definitive primary preoperative diagnosis, and that arthroscopy should not be performed without first completing a complete preoperative examination.

MR imaging of patellar retinacular ligament injuries

Seventeen patients with patellar retinacular ligament injuries were evaluated with magnetic resonance (MR) imaging. MR findings were correlated with clinical, surgical, and arthroscopic findings. The injuries involved the medial retinacular ligament in 16 of 17 patients and the medial and lateral retinacular ligament in one patient. Nine of 17 patients showed MR evidence of a patellar dislocation. In these patients, a triad of findings that included focal impaction injuries involving the lateral femoral condyle, osteochondral injuries of the medial patellar facet, and injuries of the medial retinacular ligament were seen. Seven of the nine patients with patellar dislocation injuries had frank osteochondral injuries. The injured retinaculum had an indistinct, irregular appearance associated with edema and hemorrhage. The patellar dislocations were clinically unsuspected in the initial evaluation of eight of these nine patients. In eight of 17 patients, the mechanism of injury was a patellar tendon tear (n = 1) or valgus hyperextension (n = 7). In the seven patients with hyperextension injuries, three had associated meniscal and cruciate ligament tears. MR imaging can help define patellar retinacular and associated osteochondral injuries, which may be clinically useful information.

The quantitative measurement of normal passive medial and lateral patellar motion limits

To quantify normal motion, medial and lateral passive patellar motion limits were measured in 67 high school athletes randomly selected from a group of 1340 athletes undergoing preseason physical examinations. Patellar displacement was measured at knee flexion angles of 0 degree and 35 degrees, using both a Patella Pusher (a hand-held force gauge) and a manual technique, and the results were compared. Demographic data and physical examination of the deceleration mechanism (Q angle, vastus medialis obliquus dysplasia, patella alta and baja, and valgus and varus alignment) were correlated with patellar motion limits. With the knee in extension, passive displacement of the patella averaged 9.6 mm medially and 5.4 mm laterally. In flexion, medial displacement averaged 9.4 mm and lateral displacement averaged 10.0 mm. No positive correlations were found between demographic data or deceleration mechanism examination parameters and patellar motion limits, suggesting that motion produced by the displacement force was limited by ligamentous restraints only. The clinical assessment of the passive limits of patellar motion should include examination at knee flexion angles of 0 degree and 35 degrees. The manually produced displacement was found to be more reproducible than displacement by the Patella Pusher (P < 0.05).

The patellar tendon: thickening, internal signal buckling, and other MR variants

We studied the range of appearance of asymptomatic patellar tendons and evaluated the effect of age, weight, joint effusions, and anterior cruciate ligament (ACL) tears on this tendon. One hundred and seventy-three patellar tendons in asymptomatic patients were studied at 1.5 tesla. Sagittal short and long TE images were evaluated in regard to tendon thickness, ratio of thickness of patellar to quadriceps tendons, frequency, location, and severity of intratendon signal, and frequency and severity of tendon buckling. Results were correlated with patient age, sex, weight, the presence of ACL tears, and relative volumes of joint fluid. The mean thickness of the patellar tendon was 0.52 cm. The patellar to quadriceps tendon ratio was 0.72. The patellar tendon frequently (74%) had focal areas of signal apparently within it. This signal was usually subtle, V-shaped (95%), and seen posteriorly in the proximal end of the tendon (82%). Intratendon signal was also seen commonly in the inferior aspect of the tendon (32%). This signal intensity did not increase with greater T2-weighting (99%). Buckling of the patellar tendon was a frequent asymptomatic variant (71%) but was also associated with joint effusions (p < 0.01) and ACL tears (p = 0.01). Buckling, intratendon signal, and tendon thickness increased with weight and age. Variation of the magnetic resonance appearance of the patellar tendon is frequent. Many of these changes appear to represent subclinical degeneration. Buckling of this tendon also may occur secondary to joint effusions or ACL tears.

Evaluation of the medial soft-tissue restraints of the extensor mechanism of the knee

We performed an anatomical dissection of the medial soft-tissue retinacular fibers that restrain lateral patellar displacement and found that the medial patellofemoral ligament inserts not only on the patella but also on the undersurface of the distal aspect of the quadriceps mechanism. The deep capsular layer contained substantial retinacular fibers that were associated with the medial patellomeniscal ligament. Functional studies of the relative contributions of the medial soft-tissue restraints in the prevention of lateral patellar displacement were also performed. Twenty-five fresh-frozen specimens of the knee, obtained after amputations (nineteen specimens) or from cadavera (six specimens) were tested biomechanically on a universal testing instrument. We ranked the soft-tissue restraints, in order of their relative contributions to the restraining force, on the basis of the percentage of force provided by the retinacular and ligamentous tissue that resisted the lateral displacement of the patella. The medial patellofemoral ligament, although varying in size and importance, was found to be the major medial soft-tissue restraint that prevented lateral displacement of the distal knee-extensor mechanism, contributing an average of 53 per cent of the total force. The patellomeniscal ligament and associated retinacular fibers in the deep capsular layer of the knee, which were previously thought to be functionally unimportant in the stabilization of the patella, contributed an average of 22 per cent of the total force. The previously described retinacular fibers (the patellotibial band) were functionally unimportant in the prevention of lateral displacement.