Download Distal Semimembranosus Muscle Tendon Unit and Oblique

Distal Semimembranosus Muscle
Tendon Unit and Oblique Popliteal
Ligament: Morphology and Accurate
Terminology
Taylor Delamarter
Western University of Health Sciences
COMP-Northwest
2.22.14
ABSTRACT
•
Background: Our knowledge of the stability of the posteromedial knee is evolving. The distal
semimembranosus is an important posteromedial stabilizer of the knee. Current anatomical texts
and atlases do not accurately detail the distal insertion. Journal literature commonly mentions
multiple distal insertions, one of which contributes to the oblique popliteal ligament. The purpose
of this study was to review the literature, current morphology, terminology and clinical relevance of
the distal semimembranosus muscle-tendon-unit (SMTU), and suggest alternative nomenclature.
•
Methods: Literature search was conducted on anatomical and clinical texts, atlases, journals and
websites to analyze the distal morphology of the semimembranosus muscle. Deep dissections were
performed on 31 embalmed cadavers, 56 knees in total (27Rt and 29L), identifying the distal
semimembranosus tendon morphology.
•
Results: Literature search revealed significantly inconsistent morphology of the distal
semimembranosus muscle-tendon-unit. Cadaver dissection revealed a consistent trifurcation with
three dominant expansions. Cadaver dissection also revealed an oblique popliteal
tendon/expansion, indigenous to SMTU, not a ligament.
•
Conclusion: This study provides evidence of a consistent morphology and suggests a more precise
nomenclature of the distal SMTU, which includes renaming the oblique popliteal ligament as the
oblique popliteal tendon/expansion.
Results: Cadaver Dissection
• Embalmed cadaver dissection revealed a trifurcation of the distal
SMTU at the posterior aspect of the medial femoral condyle in each
of the 56 dissected knees.
• The first identified expansion coursed in a superior oblique
direction to attach into the lateral aspect of the joint capsule
directly posterior to the lateral femoral condyle.
• The second identified expansion of the trifurcation had an anterior
course. It provided fibers into the medial meniscus and the medial
collateral ligament, and terminated into the anteroinferior aspect of
the medial tibial condyle.
• The third and terminal identified expansion of the trifurcation took
an inferior course to the posterior inferior aspect of the medial
tibial condyle, and was consistently more inferior than the anterior
limb. This limb also provided fibers to the fascia of the popliteus
muscle.
Fig. 2
Oblique
Popliteal
Tendon/Expansion
OPT
Anterior
Expansion
Inferior
Expansion
Discussion
• This study reveals a consistent trifurcation of
the distal SMTU; therefore, the authors
propose that the expansions of the
trifurcation be named the oblique popliteal
expansion (oblique popliteal tendon, not
ligament), the anterior expansion, and the
inferior expansion.
ABSTRACT
•
INTRODUCTION. The objective of this study was to investigate the ‘oblique popliteal ligament’ (OPL) and challenge its
alleged ligament status. The posterior aspect of the knee has been increasingly studied because of its clinical
relevance. Surgeons, biomechanists, physical therapists, all health care providers dealing with the musculoskeletal
system and anatomists need to have a definitive and precise understanding of the structures of the posteromedial
knee. The currently named OPL is indigenous to the distal semimembranosus (SMT); therefore, by definition is not a
ligament inserting from bone to bone. This is clinically important because of the proprioception of a tendon versus a
ligament.
•
METHODS. Literature search was conducted on texts, journals and websites regarding the formation of the OPL.
Dissection of 70 knees included macro analysis, harvesting OPL, distal SMT and LCL samples and performing
immunohistochemistry to 16 knees with antibody staining to the OPL, distal SMT and LCL.
•
RESULTS. All but one text claimed the OPL receives fibers from SMT. Macro dissection of 70 knees revealed the OPL
forming from the distal SMT tendon trifurcation (100%). Microanalysis of OPL, distal SMT and LCL samples from 16
knees demonstrated expression of nervous tissue within selected samples.
•
DISCUSSION. Woodburne stated the OPL formed from the fibers of the distal SMT tendon; however, no journals or
texts have hypothesized that this ligament is indigenous to the SMT thus, a tendon itself. Clinically it is important we
know what type of tissue for purposes of maximizing rehabilitation and surgical techniques.
•
CONCLUSION. This study suggests the OPL be considered the oblique popliteal tendon as a result of the macro and
micro evidence revealed.
Superior
Fig. 1a
L
a
t
e
r
a
l
OPL
Fig. 1b
OPL
Inferior
M
e
d
i
a
l
Deep dissections revealed that the alleged oblique popliteal ligament’s distal (medial) attachment
originated from the SMTU in 100% of 70 knees. Its proximal (lateral) attachment inserted into the
joint capsule in 39/70, bone in 11/70, and both joint capsule and bone in 20/70 knees
Fig 3
SMTU
OPL
Fig 3a: SMTU
Fig 3b: OPL
Fig 3c: LCL
Fig 4a: SMTU
Fig 4b: OPL
Fig 4c: LCL
CONCLUSION
• The macro analysis of the OPL revealed unequivocally it is indigenous to
the distal SMTU. The microanalysis using an immunohistochemistry stain
with PGP9.5 revealed a positive result for neuronal axons within both the
SMT and OPL. Further microanalysis using an immunohistochemistry stain
with β-Tubulin revealed a positive stain for neuronal axons in the SMT,
OPL, and LCL. Though the latter result leads the authors to question the
validity of differentiating tendon from ligament using this particular
immunohistochemistry stain. The macro analysis results are overwhelming
and the microanalysis reveals striking similarities in the histology of both
the OPL and SMT. The authors strongly suggest that the oblique popliteal
ligament be renamed the oblique popliteal tendon (OPT) due this macro
and microanalysis study. Clinically, this study improves terminology
accuracy and medical international language, allowing for better
understanding of successful rehabilitation methods and rationale for
current and future surgical procedures.
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