Minimally Invasive Dorsal Cheilectomy and Moberg Osteotomy for Hallux Rigidus



Minimally Invasive Dorsal Cheilectomy and Moberg Osteotomy for Hallux Rigidus


Thomas L. Lewis

Robbie Ray

Peter Lam



♦ INTRODUCTION

Hallux rigidus is a degenerative disorder of the first metatarsophalangeal joint (MTPJ) that causes substantial discomfort, as well as a decline in function and quality of life. It is common, affecting 2.5% of the population over 50 years old and disproportionately affecting females. Hallux rigidus is characterized by the formation of dorsal and peripheral osteophytes, flattening of the metatarsal head, and a reduced joint space width, giving rise to symptoms of increasing pain, dorsal tenderness, and a progressive reduction of overall mobility, especially dorsiflexion, at the first MTPJ.1

The operative treatment of hallux rigidus focuses on either joint-preserving interventions, such as cheilectomy or osteotomy of the metatarsal or phalanx, or joint-sacrificing surgery in the form of arthrodesis or arthroplasty.2 Jointpreserving operations are indicated for early stages of hallux rigidus, while arthrodesis is the gold standard for advanced stages of hallux rigidus with predictable and consistent satisfactory results in 90% of cases.3

The most common joint preservation operations include a cheilectomy, which can be combined with a Moberg osteotomy (dorsal closing wedge osteotomy of the proximal phalanx (P1) of the hallux). One biomechanical theory based on a cadaveric study showed that a Moberg osteotomy shifted the center of pressure on the first metatarsal head in a plantar direction.4 The plantar shift created by the Moberg osteotomy may lessen forces on the arthritic joint surfaces, especially dorsal articular chondral lesions.

The aim of this chapter is to review the indications, surgical technique, and literature outcomes following minimally invasive (MIS) dorsal cheilectomy and Moberg osteotomy for hallux rigidus.




♦ INDICATIONS AND CONTRAINDICATIONS

Clinical examination and radiographic studies are required to guide the surgical decision-making regarding whether to proceed with a joint-preserving or joint-sacrificing technique. Weight-bearing radiographs can be categorized using the Coughlin and Shurnas classification of hallux rigidus. Patients with a Coughlin and Shurnas grade less than 3 are potential candidates for joint preservation. Preoperative range of motion assessment is important, as surgery is not recommended for patients with first MTPJ dorsiflexion greater than 20°.

The aim of the cheilectomy and Moberg osteotomy are to increase range of motion by removing bony osteophytes that may be blocking dorsiflexion and effectively elevate the proximal phalanx by plantar subluxation of the first MTPJ. In the authors’ experience, the combination of cheilectomy and Moberg osteotomy may increase the dorsiflexion range by at least 10° to 20°.

Patients with significant pain on applied compressive force across the joint rather than predominantly pain on dorsiflexion (Coughlin and Shurnas grade 4) are unlikely to significantly benefit from joint preservation surgery and should instead be considered for joint-sacrificing surgery.


♦ PATIENT HISTORY AND PHYSICAL EXAMINATION

When taking a history, it is important to inquire as to whether more of the pain is due to rubbing of the osteophytes on shoe wear or pain with motion at the joint. For pain due to rubbing of osteophytes, shoes with a soft upper part can be useful for reducing pain, bursitis, and ulceration. For pain with range of motion, a shoe with a stiff sole or orthotics with a Morton extension or spring steel plate can limit movement at the first MTPJ, reducing inflammation and pain. Rocker sole shoes are available that combine these two factors and can be an excellent conservative measure in the early treatment of painful first MTPJ arthritis.

Evaluation of patient history is important for identifying underlying inflammatory conditions such as gout or other inflammatory arthropathies. Although these conditions do not necessarily exclude a joint-preserving procedure, patients with continued bouts of acute inflammation and pain the patient are more likely to benefit from joint arthrodesis.

Deformity should also be assessed. If there is minor axial plane deformity, an Akin or combined Akin and Moberg osteotomy may be beneficial during surgical correction. Midrange of motion pain and, more specifically, axial compression testing in a neutral position should be performed to assess for deep intra-articular pain. Although midrange pain does not preclude joint-sparing surgery, pain on axial compression in
a neutral position should push the surgeon toward joint-sacrificing surgery, as this is suggestive of central arthritic rather than dorsal impingement pain, making the patient less likely to clinically improve with joint-sparing procedures.

Range of motion should be assessed as preoperative range of movement generally dictates postoperative range of motion. In the authors’ experience, although great dorsiflexion is seen intraoperatively after dorsal cheilectomy, patients generally gain only around 10° to 20° of motion after recovery from the procedure.5

Finally, an assessment of the hallux interphalangeal (IP) joint should be performed (Figure 6.1). If the patient has hyperdorsiflexion of the IP joint, they are more tolerant of stiffness at the MTPJ and a dorsal cheilectomy without Moberg may be sufficient to improve dorsiflexion, even in a significantly stiff first MTPJ. If the hallux interphalangeal joint does not have compensatory hyperdorsiflexion, all dorsiflexion will have to come from the first MTPJ, and it may be prudent to add a Moberg osteotomy.







♦ IMAGING STUDIES

Standard weight-bearing anterior-posterior (AP), oblique, and lateral radiographs are essential to guide decision-making with regard to performing a cheilectomy and Moberg osteotomy. The lateral view should be evaluated for dorsal osteophytes in conjunction with the AP view, which is useful in showing medial and lateral osteophytes, sclerotic changes, joint-space narrowing, and subchondral cysts (Figure 6.2).

Additional cross-sectional imaging is not usually needed, but if osteochondral abnormalities are suspected, advanced imaging may be helpful. In cases of trauma, normal radiographs, or young patients, an MRI may be recommended to evaluate for chondral injury, a loose body, or a developing osteochondral defect.


♦ PREOPERATIVE PLANNING AND PREPARATION

The setup for MIS procedures is of the utmost importance in order to improve the flow and efficiency of the procedure. The main aims of the setup are as follows:



  • The surgeon should be well positioned to use the burr with their dominant hand.


  • There must be adequate space and planning to use an image intensifier or mini C-arm throughout the procedure without risking sterility or the comfort of the surgeon.


  • The nurse or surgical technician should be positioned so that they are available to pass instruments without impeding the surgeon or image intensifier.

The patient is positioned with the operative foot hanging from the end of the operating table by 6 in and the nonoperative leg frog-legged out of the operative field (unless the patient has an anterior total hip arthroplasty) in order to avoid obstructing the image intensifier. This allows for natural plantarflexion at the ankle and aids the surgeon in obtaining a true AP image of the first ray. It is also possible to achieve a true lateral view intraoperatively if the assistant externally rotates and flexes the knee. The authors do not recommend use a sandbag as the foot requires manipulation throughout MIS forefoot procedures, and a sandbag can impede external rotation, which is often required when taking a lateral radiographic image.

A right-handed surgeon should always position themselves to the left of the patient at the foot of the bed. This allows for full access to the first ray using medial incisions and puts their dominant hand in a relaxed position to operate. It follows that the image intensifier or mini C-arm should be brought in from the right of the patient so as not to impede access to the patient’s foot.

Another important aspect of imaging positioning is that the imaging machine should be arranged so that the
plate or drum is used as a table on which the forefoot rests. It is the authors’ preference to use a mini C-arm over a large image intensifier. The other important factor to consider is that many orthopedic procedures are performed in theatres with a laminar flow Perspex box, and due to the commonly performed procedures being lower limb arthroplasty, the bed is generally positioned with the feet at the edge of this box. If this is the case, the Perspex box can impede access for the imaging machine especially if it is a larger machine, and due care must be taken to position the patient deeper into the laminar flow Perspex box prior to beginning the procedure.






The nurse or surgical technician should be positioned such that they are not in the way of the surgeon and able to assist throughout the procedure. As such, for the right-handed surgeon, the authors position the nurse to the left of the patient behind the surgeon. From this position, the assistant has ample space to open their trays and have their equipment ready. The console for the MIS system and power instruments should be set up at the patient’s right hip out of the operating field.




SURGICAL TECHNIQUE


MIS DORSAL CHEILECTOMY OF FIRST MTPJ

The procedure is typically performed under total intravenous anesthesia with propofol. Once the patient is sedated, a first ray proximal digital ring block is performed using 30 mL of a combination of 1% lidocaine and 0.5% ropivacaine. A tourniquet is not used for this procedure. The skin incision for an MIS dorsal cheilectomy of the first MTPJ is made dorsomedially 2 to 3 cm proximal to the joint and adjacent to the extensor hallucis longus (EHL) tendon (Figure 6.3). This position allows for capsular release and clearance of the osteophytes from lateral to medial. The incision is made through the skin and dermis to expose the subcutaneous fat. After the dermis is cut, it is vitally important to make a safe plane down to the capsule without damaging the dorsomedial cutaneous nerve or extensor hallucis tendon.6,7

The MIS periosteal elevator is inserted with the blade of the periosteal elevator in line with the skin incision down to bone. This reduces the risk of iatrogenic injury to the dorsomedial cutaneous nerve. The elevator is then used to elevate the periosteum distally in order to reach the dorsomedial capsule. The proximal dorsomedial capsule is punctured with the periosteal elevator. The elevator is then directed intracapsularly toward the lateral aspect of the joint over the prominent dorsal osteophyte. The proximal dorsal capsule is then released from the lateral to the medial side. The capsular attachments are particularly adherent at the dorsomedial aspect, and if there is a combination of a dorsal osteophyte and medial exostosis, it is particularly important to focus on elevating the capsule here to make a clear path for osteophyte excision without any fragments adhering to the capsule. The complete release of the dorsal capsule from its attachment to the first metatarsal head is important to allow easier removal of the dorsal cortical fragments at the end of the cheilectomy. Once the dorsal capsular attachment to the first metatarsal head is fully released, the burr is inserted into the dorsal first MTPJ. The minimum size burr to use for dorsal cheilectomy
is a 2.9 or 3.1 wedge burr. The advantage of this burr is its conical shape that allows for cutting as well as grinding the bone. The primary sweep of the burr should be performed through the dorsal osteophyte, and create a plane between the osteophyte and the remaining metatarsal head. When performing a cheilectomy, the authors advocate performing a lateral to medial cut because the dorsal surface of the metatarsal is used as a guide for the burr (Figure 6.4).