Transarticular Adductor Release
January 1st, 2003
Myerson, MS, Stamatis, E, Huber, M
Abstract
Distal soft tissue release is a well established procedure as part of the correction of hallux valgus deformity. Despite its universal acceptance there is however not a uniform method of performing this procedure, nor which anatomic structures require release. Although the most common method of performing the adductor release includes a separate incision in the first web space, there are surgeons who minimize the dissection, and perform the release as a trans-articular procedure from the medial aspect of the hallux metatarsophalangeal joint. There are few anatomic studies which have studied the consistency of release with these two approaches.
We performed anatomic dissections in fifteen fresh cadaver below the knee specimens, to evaluate the efficacy of the trans-articular soft tissue release utilizing an arthroscopic blade. We hypothesized that the unique features of this blade would increase its efficacy during the trans-articular soft tissue release. Based on our observations, we recognized inherent limitations of the trans-articular approach for an adequate adductor release. We found that a transarticular lateral release including the lateral sesamoid and MTP ligaments as well as the common tendon of the adductor and lateral head of FHB insertion onto the proximal phalanx, using the arthroscopic blade, is a reproducible, safe and relatively easy technique with decreased morbidity, improved cosmesis and reduced risk of metatarsal head vascular impairment.
Introduction
Since the original description by Silver (25) in 1923, the distal soft tissue release as part of correction of hallux valgus deformity has seen several modifications (4, 9, 10, 14). These have included the specific anatomic structures which require release, imbrication, or transfer. A commonly performed method today includes release of the contracted lateral metatarso-phalangeal (MTP) joint structures (lateral capsule, lateral sesamoid ligament) as well as the adductor hallucis and transverse metatarsal ligament (TML). Release of these structures permit realignment of the proximal phalanx on the metatarsal head, preserving the fibular sesamoid and the attachment of the lateral head of the flexor hallucis brevis. (11, 12)
The distal soft tissue release as an isolated procedure has a limited capacity to correct more advanced hallux valgus intermetatarsal deformity, and this release has been popularized in combination with both proximal(3, 5, 6, 12, 13, 21,22) or distal (18, 19) metatarsal osteotomies as well as medial cuneiform-first metatarsal arthrodesis (16, 23). Once the distal soft tissue release was established as an important adjunct for the correction of the hallux valgus deformity, other authors further modified the method of exposure and release. These authors have subsequently described a trans-articular release, through a single medial incision of the MTP joint (2, 20-22, 27, 28). The benefits of such an approach were presumed to be the decreased morbidity associated with an added incision, improved cosmesis, and a reduced risk of avascular necrosis of the first metatarsal head.
Anatomical studies (8, 17) have demonstrated that both, dorsal and transarticular, approaches have failed to adequately release the lateral structures. In one of these studies (17) the authors failed to completely release the adductor hallucis in 79% (33/42) of the specimens utilizing an incision over the first web space, while in the other study (8) the authors reported a “surprising inability to fully release the adductor hallucis insertion onto the lateral sesamoid” independently of the approach. In the latter study the authors performed the transarticular lateral soft tissue release utilizing a # 15 scalpel blade, as it had been previously described (2, 21, 22, 27, 28).
The purpose of this study was to evaluate the efficacy of the transarticular distal soft tissue release utilizing an arthroscopic blade (Beaver, Arthro Lok, Becton Dickinson, NJ). The rationale of the study was that due to the shape of the blade, there would be variety of advantages using this arthroscopic blade compared to the standard no. 15 scalpel blade.
Materials and Methods
Seventeen fresh lower extremity specimens were used for study. These included four specimens with a moderate hallux valgus deformity (hallux valgus angle >35°, first-second intermetatarsal angle >15º). The rest of the specimens were free of any significant pathology involving the first metatarso-phalangeal (MTP) joint. Two of the fifteen specimens were used in a preliminary study to demonstrate the normal anatomy of the first web space and the lateral sesamoid complex as well as the steps of the lateral soft tissue release utilizing the arthroscopic blade. The skin and the subcutaneous tissues between the dorsal surface of the second metatarsal and the medial surface of the first metatarsal were removed. The interosseous musculature from the first-second metatarsal interspace was also removed for adequate visualization. The remaining fifteen specimens, including those with hallux valgus deformity, were used for the study. All procedures were performed by the same two surgeons (E.S and M.H), with no variance in the technique.
The advantages of the arthroscopic blade are: cutting edges on all surfaces of the blade, an increased length comparing to that of the no. 15 scalpel blade, and flexibility which permits bending without a likelihood of breakage (Fig 1). These features allow the blade to perform anatomic dissection which may have been difficult with a standard short, straight scalpel blade.
A single longitudinal medial incision was made at the junction of the dorsal and plantar skin, extending from the midportion of the proximal phalanx up to 2 cm distal to the middle cuneiform- first metatarsal joint. The medial capsule was dissected subperiostally from the metatarsal head and neck and the proximal phalanx. During the elevation of the plantar capsular attachments, the abductor hallucis insertion in the plantar-medial portion of the proximal phalanx as well as the soft tissues in the plantar-medial portion of the metatarsal neck containing the superficial branch of the medial plantar artery (nerve?), were carefully identified and preserved. The dorsal capsule was elevated in continuity with the periosteum exposing the dorsal aspect of the first MTP joint.
At completion of the capsular elevation the medial sesamoid could be easily retracted medially and a small retractor was utilized to provide further distraction in a plantar direction, enhancing visualization across the joint. In the absence of hallux valgus deformity and sesamoid rotation the lateral sesamoid ligament could be longitudinally incised with the blade inserted between the metatarsal head and the lateral sesamoid (Fig 2). In specimens #8, #9, #12, #15 which had a hallux valgus deformity, the lateral sesamoid ligament was not visible due to the fibular sesamoid rotation. In these specimens the arthroscopic blade was curved and it was inserted with the convex surface parallel to the articular surface of the lateral sesamoid (Fig 3). This allowed access to the lateral sesamoid ligament- which was located above the joint line- as well as adequate clearance from the metatarsal head avoiding inadvertent cartilage injury. The sesamoid ligament was always incised in a proximal to distal direction. Usually after completion of this step the lateral sesamoid could be more easily retracted medially allowing visualization of its lateral margin.
As the blade was abutting against the base of the proximal phalanx at the completion of the lateral sesamoid ligament release, it was turned 90° with the curved tip pointing distally. A gentle oscillating blade movement towards the plantar surface, and up to the level of the plantar plate, was performed to release the proximal phalangeal insertion of the common adductor hallucis and flexor hallucis brevis (FHB) tendon (Fig 4). The blade was then moved in a plantar to a dorsal direction, allowing detachment of the lateral capsule from the lateral aspect of the proximal phalanx. This detachment was preferable to a vertical capsulotomy. The hallux was now manipulated into a varus position, and although an adductor release had not been performed, adequate varus positioning of the hallux could be obtained without tension, even in the four specimens with the pre-existing deformity.
The blade was then further curved in order to allow adequate release of the adductor from the lateral margin of the lateral sesamoid. With the curved tip pointing plantarward, the blade was slid from distal to proximal, snugly attached to the lateral margin of the fibular sesamoid in order to allow access even to the most plantarly inserted adductor fibers (Fig 5). The release was completed slightly past the lateral-proximal portion of the lateral sesamoid in order to avoid inadvertent injury to the lateral head of the FHB. No attempt was made to reach and release the transverse metatarsal ligament.
At the end of each procedure, the skin and the subcutaneous tissues between the dorsal surface of the second metatarsal and the medial surface of the first metatarsal as well as the interosseous musculature from the first-second metatarsal interspace were removed. The adequacy of the release and the presence or absence of inadvertent laceration was then assessed. This included the oblique and transverse heads of the adductor hallucis, the conjoined tendon of the adductor hallucis and lateral head of FHB to the base of the proximal phalanx, the lateral sesamoid ligament and the lateral MTP capsule. Digital imaging was used for further documentation.
The first web space neurovascular bundle, the articular cartilage of the metatarsal head and the base of the proximal phalanx, as well as the lateral head of the FHB were also evaluated for the presence or absence of inadvertent injury.
Results
The results for the adequacy of the release are shown in Table I.
In all specimens the lateral sesamoid ligament, the lateral MTP capsule and the conjoined tendon to the base of the proximal phalanx were completely released. The transverse head of the adductor hallucis was completely released in nine specimens and it was found intact in one specimen. In five specimens the release was partial, with four of them having more and one less than 50% of the tendon fibers released respectively. The oblique head was completely released in 7 specimens and found intact in two. In six specimens the release was partial, with two of them having more and four less than 50% of the tendon fibers released respectively. Both heads were completely released in 5 specimens. Inadvertent injury to the lateral head of the FHB occurred in five specimens. In four of them only 25% of the tendon was lacerated, and in one specimen a major part of the tendon was involved (75%). There were no injuries to the first web space neurovascular bundle.
In specimen #7 there was a moderate cartilage injury on the metatarsal head.
The transverse metatarsal ligament was found intact in all specimens.
A careful review of Table I reveals that all inadvertent lacerations of the lateral head of the FHB occurred in combination with a complete release of the oblique head of the adductor hallucis. The results in the specimens with the hallux valgus deformity (#8, #9, #12, #15) were not dissimilar, and the release was adequate. In one specimen (#8), despite release of the oblique head, the transverse head was found intact.
Discussion
The normal anatomy of the first MTP joint and the first web space have been thoroughly described (1, 7). Stability of the first MTP joint and sesamoid complex is maintained by a combination of static and dynamic stabilizers. Static stabilization is provided by the orientation and shape of the metatarsal and phalangeal articular surfaces as well as the capsuloligamentous complex. For example, a flat or conical shaped articular surface resists the deformity of hallux valgus better than does a rounded one. The medial and lateral MTP collateral ligaments which connect the metatarsal head to the proximal phalanx provide adequate medial-lateral stability to the joint. The medial and lateral sesamoid ligaments, which connect the sesamoids to the metatarsal head, in combination with the bony configuration of the sesamoid-metatarsal head articulation provide adequate stability to the sesamoid complex. The intersesamoid ligament maintains the integrity of the sesamoid complex, while the transverse metatarsal ligament (TML) retains its constant position with respect to the second MTP volar plate. The medial and lateral hood ligaments preserve the central position of the extensor hallucis longus on the proximal phalanx.
Dynamic stabilization is provided by the balanced action of extensor hallucis brevis and longus, flexor hallucis brevis and longus, adductor hallucis and abductor hallucis muscles. The medial and lateral heads of the FHB consistently insert onto the proximal portion of the medial and lateral sesamoids respectively. The oblique and transverse heads of the adductor hallucis insert onto the proximal lateral portion of the lateral sesamoid. There, they converge with the lateral head of the FHB to create a conjoined tendon which inserts into the lateral aspect of the phalangeal base (Fig 6). Despite there is a general consensus in the majority of the reports, with respect to the later conjoined tendon anatomy, Owens et al (17) pointed that there are surgical texts (11) which present even diagrammatically an independent adductor insertion onto the proximal phalanx without indication of the attachment onto the lateral sesamoid or the conjoined tendon. This description was not confirmed in their anatomical study with 42 fresh-frozen specimens from human cadavers. Finally, Thomson (26) in an anatomic study with 22 specimens, found an extensive variability of the abductor insertion. In 19% of his specimens the abductor had a direct insertion onto the medial side of the base of the proximal phalanx, and in 19% the abductor and the medial head of the FHB had a common insertion onto the medial sesamoid. In 25% of the specimens, a slip was given off the abductor to the sesamoid before its insertion to the phalanx.
In hallux valgus deformity, there is a medial deviation of the metatarsal head, which away from the confines of the sesamoid complex, while the great toe deviates laterally. The sesamoids remain in situ, anchored by the TML to the plantar pad of the second MTP joint (1, 24). As the metatarsal head deviates further medially, the lateral sesamoid ligament pulls the lateral margin of the fibular sesamoid. The more plantarly inserted fibers of the adductor and the TML provide an opposite force, since they retain their place. This combination of forces creates a torque effect on the sesamoid, which is rotated with the articular surface towards the metatarsal head. The amount of sesamoid rotation depends on the amount of metatarsal deviation. As the lateral sesamoid rotates, the conjoined tendon of the adductor and lateral head of the FHB, arising from its lateral margin, creates a pronation effect to the great toe. The altered position of the tendons around the first MTP joint further exaggerates the deformity. In chronic deformities the adductor as well as the lateral sesamoid and MTP ligaments shorten, preventing correction of the deformities. The TML does not participate in the pathological process (1, 24).
Despite the fact that the pathoanatomy of the deformity is well understood and described, the literature discussing the distal soft tissue release is rather controversial with respect to which anatomic elements are involved in the procedure. Mann and Coughlin (9-13) recommend adductor detachment from both the lateral sesamoid and the proximal phalanx in addition to the release of the lateral sesamoid and lateral MTP ligaments. They also recommend release of the TML. Barouk (2) believes that release of the lateral sesamoid ligament and the conjoined tendon to the proximal phalanx is adequate and recommends preservation of the TML and adductor insertion to the fibular sesamoid. He also believes that the lateral MTP capsule has to be preserved and recommends release of its plantar portion only in the presence of severe deformity. Owens et al (17) caution against release of the conjoined tendon along the base of the proximal phalanx, since this may result to increased incidence of hallux varus. Miller’s description (15) is partly compatible suggesting selective detachment of the superior portion of the conjoined tendon to the proximal phalangeal base. Resch et al (19) reported on the efficacy of the lateral release involving only adductor tenotomy. Finally there are clinicians, including the current authors, who have up until the present time, released everything but the TML (5, 6, 8).
An important issue in this controversial procedure is the lack of adequate number of anatomical studies demonstrating what the efficacy of the described methods is. In one of the two existent anatomic studies in the English literature, Lin et al (8) reported a surprising inability to fully release the adductor hallucis insertion onto the fibular sesamoid independently of the use of the traditional dorsal or transarticular approach. In a similar study Owens et al (17), utilizing only the dorsal approach, reported a 79% rate of complete release of the adductor insertion onto the fibular sesamoid.
We feel that the unique features of the arthroscopic blade significantly increase its efficacy during the transarticular soft tissue release. In the presence of sesamoid rotation, the lateral edge of the fibular sesamoid lies above the MTP joint line and it is clearly impossible for a straight blade to approach and release the sesamoid ligament. An adequately curved arthroscopic blade can adopt the convexity and the concavity of the plantar articular surface of the metatarsal head and the articular surface of the fibular sesamoid respectively, allowing release of the ligament. In Lin’s study (8) all the specimens were not pathologic not allowing the authors to encounter this technical difficulty. In contrast four of our specimens had a hallux valgus deformity with considerable sesamoid rotation, in which we could evaluate the efficacy of the blade by completely releasing the lateral sesamoid ligament.
Alvarez et al (1) pointed out that “the fibrous plantar pad enshrouds the sesamoids” and that “covered by articular cartilage, the sesamoids protrude minimally through the dorsal surface of the pads”. In the presence of chronic hallux valgus deformity, it is not uncommon for the sesamoids to have osteophytes on their margins. The insertion of the adductor hallucis is wide with a significant amount of its fibers inserted plantarly onto the lateral margin of the sesamoid. The normal sesamoid and adductor insertion anatomy as well as any concomitant osteophyte formation on the lateral sesamoid make release of the adductor tendon a difficult task, due to inadequate visualization of its fibers. Clearly a straight blade cannot sufficiently approach the adductor fibers, but the most superficial, without undesirable levering against the articular surface of the metatarsal head. This difficulty was fully reflected in Lin’s study (8) where the authors faced a tremendous inability to release the adductor from the lateral sesamoid. Here again, the curved arthroscopic blade can overpass this difficulty allowing adequate adductor release. The curved tip moving over the lateral lip of the fibular sesamoid can probe and reach the adductor fibers even when these are not directly visualized. The feeling of the gradually decreased resistance during cutting allows the surgeon, in a considerable amount of cases, to indirectly evaluate the amount of release.
The ability of the curved blade to reach difficult anatomic areas enables reduced exposure. In all of our specimens we preserved the soft tissue insertion in the metatarsal neck (Fig 5), when on the other hand there are descriptions of the transarticular release with the use of a bone hook or a small retractor under the metatarsal neck retracting it dorsally (21, 22). Clearly such an extended approach jeopardizes the vascular supply to the metatarsal head from the plantar side.
Since there is evidence, based on anatomic studies (2), that the main blood supply may arise from the plantar side, this should be meticulously preserved.
Owens et al (17) noted that in feet with moderate hallux valgus deformity the insertion of the adductor was easily identified through a dorsal incision in the first web space, and that release was facilitated by the increased intermetatarsal distance. What appears to be an advantage for the dorsal approach is clearly a considerable disadvantage for the transarticular approach. With the metatarsal head displaced medially escaping from the sesamoid complex, there is decreased trans-articular visualization of the lateral border of the fibular sesamoid which remains in the web space anchored by the TML. The increased length of the arthroscopic blade significantly helped us to overpass this difficulty in four of our specimens with hallux valgus deformity where, although not complete, adequate adductor release was achieved. Our experience comes in controversy with Lin’s hypothesis (8) that in the presence of deformity transarticular release of the adductor could be easier. In their study there were no pathologic specimens, where they would probably recognize that the short, straight no.15 blade could not reach the lateral lip of the fibular sesamoid located in the intermetatarsal space.
The most interesting point with the use of the arthroscopic blade was the almost complete absence of inadvertent injuries to the articular surfaces (only one specimen had minor cartilage injury) and the neurovascular bundle. We noticed a 30% (5/15) inadvertent injury to the lateral head of the FHB but in only one of them there was more than 25% involvement of its bulk. This always accompanied a complete release of the oblique head of the adductor.
This inadvertent injury to the lateral head of the FHB did not surprise us since Lin et al (8) described a 50% (3/6) involvement during the trans-articular approach, even with inadequate release of the adductor in all of their specimens. Additionally, Owens et al (17) reported considerable difficulty (31%, 13/42 of specimens) to identify the interval between the oblique head of the adductor and the lateral head of the FHB even with the traditional dorsal approach. This resulted to inadvertent laceration of the lateral head of the FHB in 3 specimens (7%).
We did not try to release the TML because both our experience and radiographic studies (24) have shown that the “subluxation” of the sesamoids is due to the medial deviation of the first metatarsal head and that the lateral sesamoid retains its constant position with respect to the second MTP joint. Additionally, we believe that the more plantarly inserted fibers of the TML with respect to those of the adductor hallucis, could not be reached through the trans-articular approach even with the long curved arthroscopic blade (Fig 6).
The question rises is, if such a technique can be clinically applied, what are its’ potential advantages. Based on our observations we do believe that it is a safe, reproducible procedure, especially in the presence of hallux valgus deformity. Although we did not compare it to the traditional dorsal approach or to the transarticular approach utilizing a no.15 blade, a comparison with the preexisting data supports the efficacy of the arthroscopic blade. In these previous reports (8, 17) inadequate release of both adductor heads through a dorsal approach was encountered at a rate of 21% (9/42) to 100% (6/6), and through a transarticular approach at a rate of 100% (6/6). In our study the arthroscopic blade failed to completely release the adductor in 65% (10/15) of the specimens. A more detailed review of the results between the efficacy of the arthroscopic blade and the no.15 blade (8) through the transarticular approach shows 60% (9/15) and 50% (3/6) complete release of the transverse head of the adductor respectively, while the oblique head was completely released in 46% (7/15) and 0% (6/6) of the specimens respectively.
Complete transarticular release of the common adductor and lateral head of FHB tendon insertion onto the proximal phalanx utilizing the arthroscopic and the no.15 blade (8), was achieved in 100% (15/15) and 65% (4/6) of the specimens respectively. Inadvertent cartilage and soft tissue injuries were minimal with the arthroscopic blade (articular cartilage injury to the metatarsal head of specimen #7), while in the other anatomic study (8) utilizing the no.15 blade for the transarticular approach, the inadvertent injuries to the articular surfaces and even to the capsule of the second MTP joint were present in 50% (3/6) and 33% (2/6) of the specimens respectively.
Inadvertent significant laceration (more than 25%) of the lateral head of the FHB occurred at reasonable rates (6%, 1/15 of specimens) comparing to those encountered with the dorsal approach (0%) and transarticular approach (50%, 3/6 of specimens) utilizing the no.15 blade.
In one of the previous two anatomic studies (8) inadequate release of the lateral sesamoid ligament occurred in 33% (2/6) and 0% (0/6) of the specimens through the dorsal and the transarticular approach respectively, while in our study complete release of the ligament was achieved in all specimens (15/15) including those with hallux valgus deformity and sesamoid rotation.
We recognize the inherent limitations of the trans-articular approach for adequate adductor release but other anatomic studies highlighted the same limitations even with the dorsal approach. On the other hand we emphasized the advantages of the arthroscopic blade versus the no.15 blade performing this procedure transarticularly. Since there is no general consensus with respect to which anatomic elements have to be released to adequately address the hallux valgus deformity, it is clearly a matter of personal preference which technique or instrument modification should be used. Supporters of the relatively minimal lateral release including the lateral sesamoid and MTP ligaments as well as the common tendon of the adductor and lateral head of FHB insertion onto the proximal phalanx, should find that trans-articular release utilizing the arthroscopic blade, is a flexible, reproducible, safe and relatively easy technique with decreased morbidity, improved cosmesis and reduced risk of metatarsal head vascular impairment.
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