After 20 years in practice, I have found that one of the more complicated issues is the treatment of lesser metatarsophalangeal joint (MPJ) instability. The MPJ is a very complicated joint, which is connected by collateral ligaments and pulled on by multiple external and internal foot tendons. All of these can cause strain on the joint and be sources of deformity and pain.
A common problem causing instability of the lesser MPJ is a plantar plate injury. Overall, there have been significant advances over the years in repairing the plantar plate but correcting hammertoes with complicated MPJ instability continues to be challenging.
Key Diagnostic Considerations
It is essential to listen closely to patients in order to understand their concerns and needs. Not every patient needs surgery or has pain that requires extensive repair. Most patients are more concerned initially with the new and worsening pain under the metatarsal head. They will sometimes note their toe is starting to shift. Patients with more long-standing pain will often have a more severe shift of the toe and even a crossover toe syndrome (most commonly the second toe crossing over the great toe). Overall, it is vital to understand what the patient expects. A stiff but straight toe after an arthrodesis may not be what the patient needs.
Most commonly, the patient wants to be pain-free and perform his or her normal activities. However, in addition to concerns about pain and toe position, one needs to ask more subtle, specific questions of the patient. Does the patient have difficulty in all shoes or just a certain type? What activities does the patient prefer and does a stiff toe preclude that activity? These questions will ultimately help with treatment selection.
The physical examination also needs to be fairly detailed. When a dorsal drawer test reveals instability of the toe, this is a sign that the plantar plate is lax or partially torn. However, we need to ascertain more information to inform our treatment plan. Is there a tendon imbalance? Is there more weakness on one side of the toe versus the other, suggesting only a partial plantar plate tear? What is the level and rigidity of the digital contracture? Is the metatarsal head very prominent? Finally, is there a bunion deformity, causing overloading of the second MPJ?
Diagnostically, standard radiographs are a good start. The goal is to see the general position of the foot and bone architecture. Furthermore, metatarsus adductus and the level of toe deviation are also important factors along with the size and extent of any present bunion deformity.
If surgical intervention is a consideration, obtaining a magnetic resonance imaging (MRI) study of the foot can help the surgeon assess the level of plantar plate tear, check for a neuroma and also ensure the articular surfaces are not badly damaged. Plantar plate damage can be subtle. The surgeon should interpret the MRI as well, not just the radiologist. Get to know your radiologist and explain what you are looking for as the radiologist may not know what you suspect or be as familiar with the intricacies of the plantar plate.
Evaluating Non-Surgical Approaches To Plantar Plate Tears
Unless the patient has significant deformity, one should first attempt non-surgical care. For acute pain less than three months in duration, patients may respond to plantarflexory strapping of the toe and the use of a stiff shoe or boot to prevent strain. Physical therapy and oral steroids are also options. I do not recommend using a steroid injection as this can cause further damage and rupture to the plantar plate.
When it comes to more chronic and non-inflammatory pain that is greater than three months in duration, I prefer to add a platelet-rich plasma (PRP) or amniotic injection to the region to increase healing potential. Anecdotally, I have found this to be successful in early cases. Clinicians must convey to patients that strapping, the use of a boot or injection treatments will not correct the toe position. Again, this is why it is critical to understand the patient’s needs and expectations.
For many older or sedentary patients, fitting into shoes is impossible due to severe toe contracture. Strapping alone may improve this. For patients in this population who have a severe bunion and medially deviated third toe with a dislocated second toe, one might consider a second toe amputation.
Assessing Current Surgical Options For Plantar Plate And Hammertoe Repair
As I noted above, there have been significant advances in surgical repair of the plantar plate. The question is what works and what does not. I have experience with many systems, plantar and dorsal approaches, all with or without osteotomy or hammertoe correction.
The hammertoe contracture is an important deforming force. Correction of the hammertoe increases the plantar strength of the flexor tendons and helps with relocation of the toe. If there is a severe dorsal contracture, an extensor lengthening can help relax the dorsal strain. It is important to remember that if the toe is medially deviated as well, one must not neglect this during hammertoe correction. During my procedures, I prefer to preserve the length of the proximal interphalangeal joint (PIPJ) length and not use a saw. I primarily employ a cup and cone technique with a rongeur, and do subsequent rounding with a burr. I also try to keep the joint fairly tight but still maintain reducibility at the PIPJ so there is less gapping at final reduction.
My preferred implant is the Hammertoe Fixation System (Ossio), which is made out of a natural fiber material that incorporates easily into bone. There is no absorption and the material has a sticky quality, which keeps the bones from separating. It is also trimmable, allowing one to reduce length if the intermediate phalanx is smaller. Surgeons can also cut through this implant in case of revision or conversion to an arthroplasty. The implant can also go through an MRI without signal. I no longer use metal in my hammertoes as it is mainly intramedullary and is very difficult to remove without severe damage to the toe.
Salient Pearls For Assessing And Addressing MPJ Deformity And Dislocation
When correcting the MPJ, one must consider the stability of the joint, the amount of medial deviation, partial versus complete plantar plate tears and the amount of time that has passed since complete dislocation. The MRI and exam should help with decision making.
I divide my cases into mild, moderate and severe dislocations. A mild dislocation is a somewhat unstable joint with a very mild medial shift of the toe and very little dorsal contraction. A moderate case is one with a fairly lax joint on a dorsal drawer test and enough medial deviation that the great toe and second toe are touching or mildly overlapping. A severe case has significant medial deviation with crossover of the second toe or a complete plantar plate tear and dislocation at the MPJ. Each of these categories has some overlap so be prepared to treat and classify in a fluid fashion.
A metatarsal osteotomy and a possible extensor lengthening are often applicable in mild cases. I try to avoid a tenotomy because transfer of strain to the other digits may cause them to contract over time. I find extensor lengthening to be far better. The biggest pearl for my metatarsal osteotomies is to shift the metatarsal medially and shift the toe laterally, much like a bunion correction. I will, at times, imbricate the lateral capsule and collateral ligament for mild cases. In these instances, there is very minimal plantar plate tear and therefore, I find no need to repair it. It will heal during the post-surgical period and there is less stiffness of the joint without repair.
Moderate cases require plantar plate repair. Performing a metatarsal osteotomy shifts the metatarsal medially to help with repositioning the toe. One should examine and repair the plantar plate prior to repair of the metatarsal. A majority of plantar plate tears are lateral or central-lateral. I do not free up the entire plantar plate as I find this causes a great deal of scar tissue. I prefer to release the lateral plantar plate in the region of the tear, remove a triangular wedge and then utilize one of the plantar plate repair systems.
My system of choice currently is the Hat-Trick Lesser Toe Repair System (Smith & Nephew). I utilize the full repair system and pass two sutures, one on the medial side of the repair site and one on the lateral edge. I pass these two sutures through one or two holes, and hold them in place with PEEK interference fixation. More often than not, I use a single hole from lateral to medial and pass the sutures through that hole with one interference pin to stabilize the joint. The Hat-Trick system provides me with better correction of the medial deviation and less scarring. It is very rare for me to perform a flexor tendon transfer for a moderate case but I suggest being comfortable with it in case of poor plantar plate quality or if damage is apparent during repair.
A severe case either has a great deal of medial deviation or dislocation. In such cases, I find the plantar plate is either very poor quality or non-existent. For these patients, I now perform a flexor tendon transfer as I find it far more reproducible and successful in stabilizing a severe joint shift. I harvest the flexor tendon at the PIPJ prior to performing my hammertoe fusion. One then splits the tendon and pulls it medially and laterally along the proximal phalanx to the base of the toe on either side. The surgeon should place the tendon directly against the bone in order to avoid neurovascular damage before tensioning it and placing a single temporary stitch to hold it.
One subsequently positions and stabilizes the metatarsal in the osteotomy region. Holding the toe in position, the surgeon crosses the tendon ends over each other and adjusts tension on each side until the toe is stable and well-positioned at the MPJ. I use a 3-0 taper needle to place three double-pass stitches through the tendon to stabilize it. Then I tie the end sitting on the lateral side of the toe to the MPJ lateral capsule for additional stability and fine-tuning of the crossover toe correction. I do not use a K-wire across the MPJ and prefer to strap the toe with dressings for stability. You may have the patient begin MPJ range of motion at week two or three to prevent scar formation and joint stiffness.
A metatarsal osteotomy is usually, if not always, necessary as are hammertoe correction and extensor tendon lengthening. One may employ strapping and dressings to facilitate stabilization until suture removal. After removing the sutures, a toe strap should suffice. I like the Darco TAS Toe Alignment Splint (Darco) as it is very solid, can also incorporate a bunion splint and has an elastic band around the midfoot that decreases edema. However, any splint that prevents toe dorsiflexion is okay.
What You Should Know About Avoiding Post-Op Stiffness And Floating Toe
About 20 percent of patients will still have a floating toe at three to six months postoperatively and will require an in-office tenotomy and capsulotomy of the MPJ to reduce dorsal scarring and contracture. These procedures have proven to be very good adjuncts in my patients.
I find flexor tendon transfers rarely result in a floating toe but there is a bit more stiffness. As I noted above, one can have patients initiate gentle and stabilized range of motion of the MPJ with practicing of grip strength of the MPJ. Range of motion can be more aggressive in weekly increments with physical therapy highly recommended. Wrapping the toe with a Coban wrap for two to three months is essential to avoid swelling. A Coban wrap for the midfoot is helpful but far less important than it is for the toe.
Proper planning and a solid understanding of different surgical options will make plantar plate and hammertoe repairs gratifying and fairly reproducible treatments for patients. Although plantar plate repair can be difficult, it is important for the surgeon to have a comprehensive mastery of options as one procedure does not fit every patient case.
Dr. Baravarian is an Assistant Clinical Professor at the UCLA School of Medicine. He is the Director and Fellowship Director at the University Foot and Ankle Institute in Los Angeles (https://www.footankleinstitute.com/podiatrist/dr-bob-baravarian).
Dr. Baravarian has disclosed that he is a consultant for CrossRoads Extremity Systems and OSSIO.