How To Address High Intermetatarsal Angles In Bunion Surgery
Given that high intermetatarsal angles can complicate hallux valgus correction, these authors discuss key preoperative considerations, highlight important aspects of corrective procedures and provide pearls on dealing with complications and postoperative protocols.
Hallux valgus is a common condition that foot and ankle surgeons treat and it affects a wide range of age groups. As hallux valgus can affect an adolescent athlete, a middle-aged female or an elderly patient with rheumatoid arthritis, the presentation of hallux valgus can vary. Additionally, there are varying degrees of severity with the deformity. More severe deformities may limit a patient’s daily activities and cause extreme discomfort through excessive inflammation and instability in and around the metatarsophalangeal joint (MPJ).1
When we consider the severe bunion deformity and high intermetatarsal angles, we have to think beyond a simple “hallux valgus” correction. With severe deformity, often a significant widening of the first and second intermetatarsal angle is present. This can result from advanced arthrosis or instability of the first tarsometatarsal joint. In some cases, there is increased instability between the first and second cuneiforms as well, exacerbating the medial column hypermobility. Equinus contracture of the triceps surae may also be a contributing pathology and one needs to address this.
Our surgical procedures are aided by specific radiographic parameters but the clinical evaluation plays an important role as well. When evaluating these patients, it is important to treat the causative factor in order to prevent under-correction or recurrence of the deformity. If one does not address the proximal apex of the deformity with either osteotomies or fusions, the deformity with or without pain will recur. The apex of many high angle hallux valgus deformities lies at the tarsometatarsal joint. Accordingly, correction often starts there.
The original Lapidus procedure, described in 1934, aimed to address the metatarsus primus varus arising from first tarsometatarsal hypermobility.2 Therefore, it is important to thoroughly evaluate the patient clinically in order to determine the driving force of the deformity. One can address instability at the first tarsometatarsal joint and medial column with a primary arthrodesis and, if necessary, adjunctive procedures.3
Pertinent Pointers On The Preoperative Evaluation
After a thorough medical history and focused physical examination, one can determine the etiology of the patient’s hallux valgus. Adolescents with the juvenile bunion deformity have a genetic predisposition and often have significant hypermobility or ligamentous laxity. There is usually minimal pain associated with the bunion and patients do not become aware of the problem until their late teens. If they present at a younger age with a severe deformity and the growth plate is open, we try to wait until the growth plate closes in order to perform our definitive procedures. Adults often have more severe cases and concomitantly have a worse clinical presentation.
In either situation, it is important to understand the whole picture. What is driving the patient’s deformity? Which joints are involved? Determine if it is just the MPJ, the tarsometatarsal joint or the intercuneiform articulation that are involved. Is there underlying inflammatory or degenerative arthritis? Is there pes plano valgus? Ascertaining these critical aspects of the overall foot structure will determine if one needs to perform additional procedures alongside a first tarsometatarsal arthrodesis.
The use of preoperative radiographic images can be helpful in assessing the patient’s first ray deformities. One assesses the standard weightbearing anteroposterior (AP) view for the first metatarsal talar bisection angle (Meary’s angle), the intermetatarsal angle, the distal metatarsal articulation angle and the hallux valgus angle. On a weightbearing lateral view, one is able to assess Meary’s angle and first ray dorsiflexion, which are often associated with a significant gapping at the plantar aspect of the first tarsometatarsal joint.
So what is a high intermetatarsal angle? Traditionally, this is any angle above normal or 8 to 10 degrees. However, from a clinical standpoint, intermetatarsal angles break down into mild, moderate and severe. For this article, we chose to focus our attention on the intermetatarsal angles measuring 18 degrees and higher. What is considered a “high angle” is often surgeon specific, based on one’s experience and procedure selection.
Some authors cite the unreliability of the intermetatarsal angle in choosing the appropriate procedure for hallux valgus correction.4-6 We agree and recommend a combination of radiographic and clinical exams to choose the corrective procedure. A distal metatarsal articulation angle above normal or greater than 15 degrees is often a consequence or sign of a chronic deformity, and usually necessitates an additional distal metatarsal procedure (e.g. Reverdin osteotomy).
The last angle to take into account is the hallux valgus angle, which is often greater than 30 degrees in severe deformities. This high angle is also associated with a valgus rotation of the digit with assistance from the pull of the flexor hallucis longus tendon. One can usually address this last with a proximal phalangeal osteotomy such as an Akin osteotomy.
The other aspects of preoperative planning are patient goals and expectations. The goals of surgical correction are twofold: reduction in pain and deformity correction. One should also consider cosmesis. Formally addressing how one aims to reduce the deformity, realign the hallux and maintain the correction are all important aspects of the preoperative conversation.
A Step-By-Step Guide To The Surgical Approach
We utilize a regional popliteal nerve block and sedation for pain control and patient satisfaction. The procedure occurs with the patient supine and a small bump under the patient’s ipsilateral buttock for slight internal rotation of the extremity. A thigh tourniquet is preferable to decrease the muscular contraction that sometimes happens with the use of ankle or calf tourniquets.
First, make a 3 cm incision medial at the first MPJ, taking care to avoid and protect the dorsal medial cutaneous nerve. After retracting neurovascular structures and exposing the capsule, make an inverted L capsulotomy parallel to the first metatarsal. The key here is to have the apex of the “L” at the level of the joint so one can visualize the hypertrophic medial eminence and, if necessary, later perform a linear capsulorrhaphy. Then perform an exostectomy of the medial first metatarsal head. We recommend doing this with a very shallow resection at this stage. After correcting the proximal deformity, there is often little resection of the medial head that is necessary.
Proceed to make a 1.5 cm incision in the first intermetatarsal space at the level of the MPJ. Carry dissection down to the level of the deep transverse metatarsal ligament. Carefully transect this ligament. Utilizing a Weitlaner for retraction allows for a slight stretch on this ligament and uncoupling of the adductor head as well. After transecting the lateral metatarsal-sesamoidal ligament and the oblique head of the hallux adductor, one is able to visualize the fibular sesamoid fully while putting an adduction and varus stress on the hallux. Having already performed the medial capsulotomy, the surgeon can appreciate the amount of sesamoid reduction that one needs to maintain. As a general rule, once the lateral release is complete, adduction pressure on the medial head should create reduction of the sesamoid malposition and alignment of the first MPJ.
Finally, make a third 3 cm incision dorsomedial to the first tarsometatarsal joint. Again, the medial dorsal cutaneous nerve lies within the subcutaneous tissue plane. Identify and retract the nerve. While staying medial to the extensor hallucis longus, identify the joint and elevate the dorsal ligaments and periosteum. Utilize a Hintermann distractor with two Steinmann pins to obtain appropriate visualization of the plantar and lateral aspects of the deep joint. We routinely use a combination of curved osteotomes, curettes and a rongeur to resect the cartilage from the metatarsal and medial cuneiform. Then fenestrate the subchondral plate and fish-scale it with a drill bit and a quarter-inch osteotome.
When there are severely widened deformities, perform a more aggressive preparation of the lateral first tarsometatarsal joint to allow reduction of the high angle deviation without causing excessive shortening from wedge resection. Also, if significant first and second ray instability are present, take care to prepare the adjacent cortex on the medial aspect of the second metatarsal with a curette and drill. This allows for scarring in and around the first and second metatarsal base, and aids in sagittal plane control and reduction. A study of 77 patients showed a 30 percent incidence of an accessory intermetatarsal facet between the first and second metatarsal bases.7 This occurred in a higher incidence in first metatarsals with an increased medial obliquity of the first tarsometatarsal joint.
Then place a tenaculum reduction clamp on the dorsomedial aspect of the first metatarsal and around the second metatarsal neck. Close the clamp while recreating the windlass mechanism and dorsiflexing the hallux on the metatarsal, thereby plantarflexing the first ray at the first tarsometatarsal joint. Placing the clamp dorsomedial on the first metatarsal will also facilitate a derotational varus force on the first metatarsal. With the tenaculum, the surgeon can “dial in” the amount of reduction and visualize this via fluoroscopy. Take care not to create a negative intermetatarsal angle.
At this point, the surgeon is ready to apply fixation to stabilize the correction and facilitate fusion of the first tarsometatarsal joint. Based on clinical experience, it is our preference to use a combination of a compression lag screw and locked plating for fixation. If it is the surgeon’s judgment that the instability is just localized at the first tarsometatarsal joint and correction has occurred, place screw fixation across just the tarsometatarsal joint and apply the plate dorsomedially.
However, in most instances, we prefer to stabilize the first tarsometatarsal joint and also reduce the first ray into the stable second cuneiform to gain additional intermetatarsal angle correction and stability of the reduction. One would intentionally angle the lag screw obliquely across the first tarsometatarsal and into the second cuneiform to facilitate this.8,9
Starting at the midline of the medial flare of the first metatarsal about 2 cm distal to the tarsometarsal, direct the screw to the proximal lateral corner of the second cuneiform. One can visualize this on fluoroscopy and place the screw in typical lag fashion. The typical screw length is in the 34 to 42 mm range. While maintaining the guide wire in the screw, one can see where to avoid placing the locking neutralization plate. We routinely use locking plate technology in this procedure for added stability and earlier weightbearing.10-14 After placing the locked plate, we then remove the tenaculum and assess the intermetatarsal correction on fluoroscopy. At this time, if the metatarsal is not reduced over the sesamoids, one can manually assess the relocation of the sesamoids with medial capsule traction.
What if the intermetatarsal angle is not reduced after removing the tenaculum? First, check the interfragmentary screw placement. Make certain you are capturing the first metatarsal and have not fractured the base of the metatarsal. Proceed to utilize fluoroscopy to ensure you have placed the plate appropriately across the joint. It is easy to mistakenly place the plate too distal and lateral, and one has to correct this if the distal screws are not purchasing bone.
If there is proper fixation placement and the reduction is still not adequate, we often utilize an intermetatarsal lag screw from the base of the first metatarsal into the base of the second metatarsal. Take care not to overtighten this screw for it can easily create a hallux varus. After obtaining tarsometatarsal reduction and when the sesamoids are easily reducible, one may still need to perform an Akin procedure to gain final reduction of the hallux on the metatarsal. This is often the case with severe deformities.
Key Insights On Closure And Postoperative Protocol
Closure then begins with absorbable sutures on the medial first metatarsophalangeal capsule. Close all incisions in layers with absorbable sutures and skin with subcuticular sutures. Then use sterile dressings and place the patient in a non-weightbearing splint.
Our preferred postoperative protocol for Lapidus arthrodesis has changed over the years as more evidence has emerged for early weightbearing.14 Patients wear a non-weightbearing splint until the first postoperative visit at six days and subsequently wear a weightbearing tall fracture boot for four to six weeks. One should then reassess the patient and transition him or her to a shoe over the next four weeks.
When it comes to severe deformity correction, we offer the following take-home points.
* Assess more than the intermetatarsal angle.
* Perform an adequate distal soft tissue procedure.
* Use a tenaculum and windlass mechanism to maintain reduction.
* Our preferred method of fixation is a combination of a first metatarsal-second cuneiform lag screw and medial neutralization (locked) plate.
* Do not remove the clamp until the plate is in place.
Severe bunion deformities with an associated high intermetatarsal angle are challenging and surgeons should not take them lightly. Multiple procedures are often necessary to reduce the deformity fully and maintain correction.
Dr. McAlister is a Fellow of the Orthopedic Foot and Ankle Center in Westerville, Ohio.
Dr. Hyer is a Fellow of the American College of Foot and Ankle Surgeons, and serves on its Board of Directors. He is the Fellowship Co-Director of the Orthopedic Foot and Ankle Center in Westerville, Ohio.
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11. Klos K, Gueorguiev B, Mückley T, et al. Stability of medial locking plate and compression screw versus two crossed screws for lapidus arthrodesis. Foot Ankle Int. 2011; 31(2):158-63.
12. Scranton PE, Coetzee JC, Carreira D. Arthrodesis of the first metatarsocuneiform joint: a comparative study of fixation methods. Foot Ankle Int. 2009; 30(4):341-5.
13. Saxena A, Nguyen A, Nelsen E. Lapidus bunionectomy: Early evaluation of crossed lag screws versus locking plate with plantar lag screw. J Foot Ankle Surg. 2009; 48(2):170-9.
14. Blitz NM, Lee T, Williams K, et al. Early weight bearing after modified lapidus arthodesis: a multicenter review of 80 cases. J Foot Ankle Surg. 2010; 49(4):357-62.
For further reading, see the online exclusive “Key Pearls For Performing Bunion Surgery” at http://tinyurl.com/c36vywo .