Sharing insights from the literature as well as their own clinical experience, these authors discuss anatomical considerations, biomechanical principles and patient factors that go into central metatarsal osteotomies. They also offer proactive tips on reducing the risk of complications such as dorsal contractures and floating toes.
Podiatric surgeons typically perform lesser metatarsal surgery to address local or global metatarsal deformities. The majority of the deformities are length and/or sagittal plane deviations. The anatomic declination of the metatarsals makes the delineation difficult as length affects the sagittal plane position. Structural metatarsal deformities can include elongated, shortened, elevated or depressed metatarsals. Occasionally, these deformities can translate into pain, which can be secondary to the local metatarsal deformity or referred from an adjacent metatarsal.
Metatarsalgia is one of the most common pedal complaints. Metatarsalgia has a multifactorial etiology, which can range from structural metatarsal deformities to local or systemic disease. For the purposes of this article, we will focus on the structural deformities.
Researchers have shown that conservative treatment can be of benefit for metatarsalgia.1 These modalities include but are not limited to shoe modification (padding, metatarsal bar), orthotics, nonsteroidal anti-inflammatory drugs (NSAIDs) and palliative care. One should attempt conservative care for three to six months prior to considering operative treatment. The majority of cases respond well to these treatment modalities.
The biomechanics of metatarsalgia are secondary to load transmission through the metatarsal heads. There is usually abnormal load or pressure on one or more of the metatarsal heads, and this causes overload and subsequent pain. In normal stance, this pressure should be evenly distributed on all five metatarsal heads. The first metatarsal head supports twice as much force as any of the lesser metatarsals.2 The pressure transfer during the gait cycle tends to focus on the metatarsal heads for 30 to 55 percent of the gait cycle.2,3 The second and third metatarsals are relatively locked into position through their articulation at the Lisfranc’s joint. This explains why first ray pathology (hallux valgus, first ray hypermobility, Morton’s foot) can lend itself to central metatarsalgia.
In terms of evaluating metatarsal length and sagittal plane deviation, weightbearing radiographs are still considered the best method. The AP and sesamoid axial views are the most important. As we noted earlier, all of the metatarsal heads should purchase the ground in normal stance. The axial view can depict this scenario. The AP view is best to access the length pattern and the parabola.
Some uncertainty still exists in regard to determining the “normal” length pattern.4 Most believe the first and second metatarsals are equally the longest, and they are followed by the third, fourth and fifth metatarsals. Maestro demonstrated this in his study using the “Maestro Line,” a line from the center of the fibular sesamoid perpendicular to the longitudinal bisection of the second metatarsal.5 According to Maestro, this line should pass through the fourth metatarsal head.
Pertinent Anatomical Considerations
The anatomy of the lesser metatarsals is an important consideration when planning surgery. Osteotomies in the metaphysis heal more predictably than diaphyseal osteotomies, which tend to take longer to heal. This is related to the vascular anatomy and the anastomosis that exist in these regions. The dorsalis pedis (via the arcuate artery) and the posterior tibial artery (via the plantar arch) run through the intermetatarsal space and form a dense network of anastomosed vessels at the region of the metatarsal head both dorsally and plantarly. Nutrient arteries run along the cortex of the metaphysis around the capsular insertion. One must take caution to avoid stripping the capsule as this could result in damage to these vessels and increase the risk of avascular necrosis.
The main goal with the surgical procedure is to “normalize” the length pattern or to decrease the prominence of the metatarsal. One can do this by shortening and/or elevating the metatarsal distally. The amount of correction must be precise. If there is too much correction, the possibility of transfer lesions exists. If there is too little correction, the patient may have recurrence. The surgeon must pick the proper procedure and understand how much correction is necessary. Diligence is required as these procedures can be technically demanding and adherence to a strict postoperative protocol is paramount to successful outcomes.
Ensuring The Right Procedure For The Right Patient
Let us take a closer look at central metatarsal osteotomies. There are more than 40 separate procedures for the lesser metatarsals.6 These procedures include: metatarsal head resection; partial/total condylectomies; base osteotomies; midshaft osteotomies; metaphyseal osteotomies; and even “peg and hole” type procedures. Although each procedure has its merits, we prefer the Weil-type osteotomy and double oblique proximal osteotomy.
However, the premise of the article is to specifically discuss our pearls for successful central lesser metatarsal surgery regardless of procedure choice. We have found that these pearls facilitate successful outcomes in our experience. Although some of the following pearls may seem redundant in the eyes of many surgeons, we must remind ourselves of basic principles regularly.
• We have all heard the cliché: We don’t treat X-rays, we treat patients. As a consequence, it is vital to understand the patient’s concerns and consider a surgical plan after discussing these concerns. One must ensure substantial clinical and intraoperative assessment. Surgeons can reduce the risk of complications by having a thorough understanding of the deformity and the patients’ actual complaints. Trust will be lost if there is not a mutual understanding between the patient and doctor as to the necessity of a procedure.
• When it comes to determining whether patients are good surgical candidates, one should assess the patient’s overall health status as well as his or her ability to be adherent with any post-op protocols. Ensuring proper patient selection in this regard can help promote positive and successful outcomes.
• The patient’s lifestyle can impact the choice of procedure. There is greater tendency of women developing metatarsalgia and this may be simply attributed to wearing high heeled shoes. As a consequence, any form of equinus can further incur increased sub-metatarsal head pressure.
Keys To Addressing The Metatarsal Parabola
• To fully appreciate the metatarsal parabola aside from perioperative and clinical observation, the use of an intraoperative C-arm can be beneficial in obtaining the appropriate metatarsal parabola.
• In addition to ensuring the second metatarsal is slightly longer or equal to the first metatarsal, the third metatarsal should be approximately 4 mm shorter than the second metatarsal, the fourth metatarsal should be approximately 6 mm shorter than the third metatarsal and, finally, the fifth metatarsal should be approximately 12 mm shorter than the fourth metatarsal.4
Proactive Pointers For Minimizing Complication Risk
• One must strive for meticulous dissection and avoid extensive capsular stripping in order to preserve essential anatomy. This includes reflection and reapproximation of the periosteum, neurovascular structures, lumbricals and interossei. If one does not preserve the vessels around the metatarsal heads stemming from branches from the dorsalis pedis and posterior tibial artery respectively, this can contribute to delayed union, metatarsal head necrosis, etc.
• When performing a Weil osteotomy, we prefer to have an osteotomy cut parallel to the weightbearing surface in order to avoid a plantarly displaced metatarsal head.
• Barouk has suggested there is anastomosis between the flexor digitorum longus and flexor hallucis longus.7 If these tendons are not in synchronization, it can lead to a claw toe deformity. Therefore, it is suggested to shorten the first metatarsal as an adjunct to the second or release/dissect this particular anastamosis.
• An extensor digitorum longus (EDL) lengthening is recommended with a decompression osteotomy, such as the Weil osteotomy, in order to avoid dorsal contracture and/or claw toe deformity of the associated lesser digit.
• Another possible explanation of the floating toe problem is overcorrection of the lesser digits after proximal interphalangeal joint (PIPJ) fusion. When it comes to hardware for PIPJ arthrodesis, we prefer bioabsorbable pins. An advantage of this form of fixation is the ability to bend/manipulate the toe perioperatively to facilitate physiological correction for a more “natural” appearance and to further allow the toe to achieve ground purchase. Some authors have shown that performing a PIPJ fusion with a Weil osteotomy increases the risk of a floating toe.8
• When performing an isolated metatarsal osteotomy, we typically make longitudinal curvilinear incisions. This aids in reducing potential dorsal contractures.
• If you have to perform more than one osteotomy, using a dorsal transverse incision can help avoid dorsal contractures of the lesser digits. One should exercise caution with a diligent skin incision that avoids all neurovascular structures. Once you have adequate exposure, there is an excellent view of the adjacent metatarsal heads to assess for the metatarsal parabola. In addition to clear observation of the entire anatomy, when the lesser digits are held in plantarflexion, the neurovascular structures coursing longitudinally are plantarly displaced between the respective metatarsals. Therefore, one can further reduce the risk of any potential damage to the anatomy while performing surgery.
• Although shifting the metatarsal head medial or lateral on the shaft can correct lesser digit transverse deviation, one must avoid rotation of the metatarsal head. There has been discussion among surgeons as to the use of two points of fixation and/or use of a temporary K-wire to hold the osteotomy while placing a cannulated screw of choice. However, there is a new metatarsal clamp from Arthrex that aids in maintaining stability, preventing metatarsal head rotation and further allowing access for one screw fixation. Be sure to avoid plantar stripping of the capsule as we previously mentioned.
Essential Post-Op Pearls
• Strapping the lesser digit(s) in plantarflexion for four to six weeks postoperatively is strongly encouraged to further reduce the risk of the dreaded floating toe phenomenon.
• One can further minimize the risk of a floating toe by utilizing physical therapy modalities postoperatively. These physical therapy methods include: passive manipulation of the digit (s) in plantarflexion; dorsal incision massage; and tiptoe gait and stance to encourage toe-ground purchase.
Other Considerations To Help Facilitate Optimal Outcomes
• Intraoperative evaluation of the metatarsal position is essential. One can assess metatarsal length on the C-arm with loading of the foot. There are two methods for evaluating the sagittal plane position. The first is with direct palpation of the metatarsal heads with the hindfoot and ankle in a neutral position. The second method involves repeating the first method with the metatarsophalangeal joints dorsiflexed to simulate late stance phase heel off.
• It is important to understand the biomechanics of the osteotomy. For instance, surgeons should perform a Weil type osteotomy for digital decompression and instances of an abnormal metatarsal parabola. If there is a sagittal plane deformity with a plantar lesion, the osteotomy will require dorsal wedge resection for elevation. Melamed and colleagues noted that the only way to shorten and not plantarly displace the metatarsal was by using a Weil osteotomy with 5 mm of shortening and removal of a dorsal wedge.9 Adelaar and co-workers showed no reduction in load transmission following a Weil osteotomy.10
• In our hands, decompression osteotomies rarely lead to MPJ stiffness. Some authors are against anatomic capsular reconstruction and believe it lends itself to capsular contraction and stiffness of the joint.11 Surgeons can manage contracture with a percutaneous extensor tendon release and subsequent splinting of the digit in plantarflexion.
Depending on the severity of the deformity, soft tissue structures will adapt to the function the patient requires. This can potentially create noticeable inequality between osseous length and soft tissue elasticity. In other words, the physiological tension of the soft issue structures, as a result of a shortening osteotomy, may be diminished. This can differ in all patients depending on their respective function levels and physical demands.
Due to the nature of decompression osteotomies and their effect on the respective digits, we as surgeons should question whether all hammertoe corrections are overperformed or are sometimes even necessary. The harmony between soft tissue structures (intrinsics and extrinsics) and their associated osseous structures may be violated by surgical overcorrection.12 Therefore, perioperative assessment will help negate potential postoperative complications.
A thorough understanding of normal and pathological biomechanical principles is a prerequisite when considering any surgical intervention. As we noted previously, there are many documented surgical procedures and despite the prevalence of this pathology in our offices, the technical difficulty and finite details required make the lesser metatarsal osteotomy one of our most complex procedures.
The Weil-type osteotomy and proximal closing wedge oblique osteotomy are our most widely performed lesser metatarsal procedures. Whether one procedure is better than the other comes down to the specific requirements of both the patient and doctor. As with most surgeries, the patients’ health and compliance is of massive importance. This ultimately is what contributes to successful outcomes.
Dr. Akhtar is an Associate of the American College of Foot and Ankle Surgeons. He is in private practice in Howell, N.J.
Dr. Diiulio is an Associate of the American College of Foot and Ankle Surgeons. He is in private practice in Crestview Hills, Ky.
Dr. Cicchinelli is a Fellow of the American College of Foot and Ankle Surgeons. He is a faculty member of the Podiatry Institute. Dr. Cicchinelli is in private practice in Mesa, Ariz.
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