Thomas P. San Giovanni
DEFINITION
Hallux rigidus is an arthritic condition of the first metatarsophalangeal (MTP) joint. It is the most common form of arthritis affecting the foot.
An estimated 2% to 10% of the general population displays varying grades of hallux rigidus.1,7,9
ANATOMY
Hallux rigidus involves the first MTP joint, which comprises the articulation between the first metatarsal head, the proximal phalangeal base, and the sesamoid complex.
Although the proximal phalanx is often involved, the predominant disease involves the dorsal aspect of the metatarsal head with articular cartilage loss and dorsal osteophyte formation (FIG 1).
PATHOGENESIS
The cause of hallux rigidus is controversial and is likely multifactorial.
Predisposing or associated factors cited in the literature include flat, square-shaped metatarsal head morphology; metatarsus adductus; hallux valgus interphalangeus; positive family history with bilateral condition; and trauma.1,9
Isolated or repetitive injury may cause damage to the dorsal aspect of the joint, which leads to altered mechanics (compressive and shear forces increased dorsally). Progressive deterioration of the articular surface, osteophyte formation, and joint contracture ensue.
FIG 1 • A. Lateral diagram depicting articular cartilage loss and osteophyte along the dorsal aspect of the first metatarsophalangeal joint. B. Frontal view showing dorsal articular cartilage loss extending into the central aspect.
NATURAL HISTORY
In its early stages, articular cartilage loss is present along the dorsal aspect of the first metatarsal head. As the condition progresses, articular cartilage loss extends to the central aspects of the metatarsal head and lastly the plantar aspect (FIG 2).
Although less involved, the proximal phalanx will exhibit varying degrees of articular cartilage loss and dorsal osteophyte formation.
The natural history of hallux rigidus is one of gradual, progressive worsening.9
FIG 2 • Varying degrees of articular cartilage loss of the first metatarsal head in hallux rigidus. Radiographic findings often underestimate the extent of disease seen intraoperatively.
FIG 3 • A. Dorsal view of foot in hallux rigidus. Shoe wear may cause irritation over the dorsal bony prominence. B. Limited dorsiflexion is noted on the clinical examination.
PATIENT HISTORY AND PHYSICAL FINDINGS
Patients present with complaints of dull, aching, and at times sharp pain along the dorsal aspect of the joint associated with weight-bearing activities.
Complaints of stiffness and development of a painful dorsal bony prominence are characteristic of the condition.
The physical examination reveals tenderness overlying the first MT head with a notable dorsal bony prominence, along with limited range of motion of the first MTP joint, particularly dorsiflexion (FIG 3).
The examiner should assess for pain on midmotion, crepitus, positive first MTP grind test, and plantar tenderness overlying the sesamoids, which represents more extensive disease.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Weight-bearing AP, lateral, and oblique views are obtained. The examiner should assess for joint space narrowing, presence of dorsal osteophytes, and joint congruity.
In a radiographic grading system often used in the literature, grades 1, 2, and 3 signify the percentage of joint space narrowing, the presence or absence of subchondral sclerosis or subchondral cyst, and the degree of osteophyte formation (Table 1, FIG 4).4
FIG 4 • A. Grade 1 hallux rigidus. B. Grade 2 hallux rigidus. C. Grade 3 hallux rigidus. D. Lateral view of hallux rigidus.
CT and MRI advanced imaging studies are generally not obtained. Evaluation with MRI may occasionally be indicated if the radiographs appear normal but suspicion remains for a central osteochondral defect of the metatarsal head. CT scan is occasionally obtained to assess or confirm the presence of severe metatarsosesamoid involvement, signifying advanced disease.
DIFFERENTIAL DIAGNOSIS
Gout
Other systemic arthritides (rheumatoid arthritis, psoriatic arthritis, seronegative arthropathy)
Posttraumatic arthritis
Arthritis associated with severe hallux valgus or sequelae status post hallux valgus surgery
Central osteochondral defect, first metatarsal head
Avascular necrosis of the metatarsal head
Sesamoiditis or sesamoid-related pathology
Septic arthritis
Soft tissue or bone neoplasm
NONOPERATIVE MANAGEMENT
Nonoperative management of hallux rigidus includes shoe wear modifications, use of anti-inflammatories, orthotics with a Morton extension or carbon fiber plate orthotic, and rarely intra-articular cortisone injections.
SURGICAL MANAGEMENT
When nonoperative management fails to provide adequate symptom relief, the patient and surgeon are faced with choosing from an array of surgical procedures.
The most common performed procedure for hallux rigidus is a cheilectomy.
Simple cheilectomy has been proven successful for early stages of hallux rigidus,1,2,4,9 although cheilectomy outcomes are less promising with advanced disease, particularly grade 3.1,7,8 As articular cartilage loss extends to the central and plantar aspects of the joint, the joint deterioration progresses beyond that which a cheilectomy would be expected to adequately treat.
Alternative or adjunctive procedures to cheilectomy include:
Moberg dorsal closing wedge phalange osteotomy10,14,15
Various first metatarsal decompression osteotomies14
Soft tissue interpositional arthroplasties and modified oblique Keller resection3,7
Proximal phalangeal base hemiarthroplasty11,16
Metatarsal head resurfacing hemiarthroplasty5,12,13
Total great toe arthroplasty6
First MTP arthrodesis1,9,11
Historically, a first MTP arthrodesis has proven to be the most reliable procedure for providing pain relief in advanced stages (grade 3).1,11 However, many patients find the thought of complete motion loss in exchange for pain relief unacceptable and prefer not to undergo a fusion procedure for this reason alone.
Alternative surgical solutions that maintain some degree of motion and provide pain relief have been sought in an effort to address this patient subset with advanced disease who refuse to undergo fusion. This has led to the development of various arthroplasty techniques, including soft tissue interposition or implant arthroplasty.
One such implant is the Arthrosurface HemiCAP with the technique described below.
Preoperative Planning
History and physical examination are performed with particular attention to the location of pain, mid-range motion pain, or significant symptomatic sesamoid involvement.
Range of motion and active and passive dorsiflexion and plantarflexion are recorded preoperatively.
Routine weight-bearing radiographs are assessed for the presence of dorsal osteophytes, the degree of joint space narrowing, joint alignment and congruency, metatarsal length, and sesamoid pathology.
Careful preoperative discussion regarding the patient's goals and expectations are paramount in determining whether individual goals will be met by the procedure. A discussion of the risks and alternative procedures, in particular discussion regarding arthrodesis, is important.
Positioning
The patient is positioned supine with a bump under the ipsilateral hip to rotate the foot to neutral.
A tourniquet is applied; however, we prefer not to use a tourniquet during the case if possible. Excellent hemostasis is achieved on the approach and leads to a drier wound on closure. We believe that postoperative swelling from hemarthrosis or hematoma formation contributes to the early motion loss seen during the early postoperative period.
Approach
A dorsal longitudinal incision is made centered over the first MTP joint.
FIG 5 • Dorsal longitudinal incision. The capsulotomy is done medial to the extensor hallucis longus tendon and the tendon is retracted laterally.
The extensor hallucis longus tendon is identified and retracted laterally (FIG 5).
Sharp dissection is carried down just medial to the extensor hallucis longus tendon and a dorsal longitudinal capsulotomy is performed with soft tissue dissection performed subperiosteally along the medial and lateral aspects of the first metatarsal head.
If a large proximal phalangeal base dorsal osteophyte is encountered upon approach, the phalangeal osteophyte is excised at this time. The metatarsal head osteophyte may be left until the implant is placed for excision at the end of the procedure.
Plantarflexion of the hallux exposes the metatarsal head, and extensive articular cartilage loss is assessed.
To release the plantar capsular joint contracture, a curved (McGlamry or similar) elevator can be passed between the sesamoids and plantar metatarsal head as long as this can be performed carefully without causing iatrogenic injury.
TECHNIQUES
GUIDE PIN PLACEMENT FOR HEMICAP
Obtain complete visualization of the metatarsal head with hallux plantarflexion.
Place the centering spherical guide for the 15-mm HemiCAP on the metatarsal head with the feet of the guide in a superior–inferior position. A 15-mm guide is used typically; only on rare occasions is a 12-mm guide used as an alternative with an anatomically small head.
The perimeter of the guide should not violate the metatarsal–sesamoid complex, and its inferior border is generally seated just above the crista. Avoid malplacement of the guide pin by plantarflexing the guide as necessary to adjust for normal inclination of the metatarsal shaft.
Place the centering guide pin on the metatarsal head in line with the long axis of the metatarsal shaft and verify its position on AP and lateral fluoroscopic views. Adjust the guide pin as necessary to obtain correct placement (TECH FIG 1A–C). Pay particular attention to the guide pin lateral view, for there is a tendency to underestimate the degree of inclination of the metatarsal shaft; parallel to the long axis of the shaft is the desired position. Adjust the pin before proceeding.
Use a cannulated drill over the guide pin and drill to depth so that the proximal shoulder of the drill bit is flush with the articular surface (TECH FIG 1D–G).
TECH FIG 1 • Guide pin placement. A. Intraoperative picture of spherical guide placement just above the crista of the first metatarsal. B. AP view of pin placed in line with the long axis of the first metatarsophalangeal shaft. C. Lateral image of pin placed parallel to the long axis of the metatarsophalangeal shaft. The surgeon can drop his or her hand as necessary to match the inclination of metatarsal and midline within the shaft. D. A cannulated drill is used over the guide pin. E. The proximal end of the drill bit should stop flush with the remaining articular surface. F. Intraoperative view of cannulated drill. G. Intraoperative view of drill's proximal end stopping flush with remaining joint line surface.
DRILL HOLE AND PLACEMENT OF TAPER POST SCREW
Tap the drill hole to the etched line.
Place the tapered screw of the HemiCAP implant, gaining purchase within the distal metatarsal bone. Bring the line indicator on the screwdriver just flush with the depth of the remaining articular surface level (TECH FIG 2).
TECH FIG 2 • A. A tap is used within the first metatarsal head, stopping at the etched line on the driver when flush with the plantar articular surface. B. A taper post screw is placed to the etched line when flush with the joint surface. C. Intraoperative use of tap. D. Intraoperative screw placement. E. The screw is stopped when the etched line is flush with the remaining joint surface.
DEPTH AND METATARSAL HEAD SURFACE MEASUREMENTS
Remove the guide pin and place the trial button cap to confirm the correct depth of the screw. Place the peak height of the trial cap flush or slightly countersunk to the level of the existing articular cartilage surface. The depth can be adjusted simply by either advancing or backing out the screw, with each quarter-turn accounting for 1 mm.
Place the centering shaft pin through the cannulated portion of the screw to act as a centering point for measuring the radii of curvature of the metatarsal head at four index points. This measures the geometric shape of the metatarsal head, assessing superior, inferior, medial, and lateral dimensions.
Slide the contact probe device through the centering pin; this measures the distance at these four points pivoting at 90-degree intervals (TECH FIG 3). Record the numbers and choose the closest match to the provided implant size. Note: Choose the largest number measured in the superior and inferior and medial and lateral directions.
Remove the centering shaft pin and place a standard guide pin back within the cannulated portion of the screw.
TECH FIG 3 • The guide pin is replaced with a wider centering shaft pin. A contact probe is then used to measure the dimensions of the metatarsal head so the proper implant size can be chosen.
SURFACE PREPARATION OF METATARSAL HEAD
A circular surface reamer is then used (TECH FIG 4). The proper size is the largest size measured in either the superior–inferior or mediolateral directions. For example, if superior–inferior measures 3.0 mm and mediolateral 2.0 mm, then use a 3.0-mm circular reamer. Note: It is important to start the reamer before contacting the bone to avoid the remote chance of uncontrolled metatarsal bone blowout if poor bone quality is noted. The depth of the reamer is controlled, for it will stop on its own when contacting the screw.
TECH FIG 4 • A. A circular reamer is used over the guide pin. There is a built-in stop when it reaches the edge of the screw. B. View after reaming for bone preparation for the HemiCAP. The screw is seen within the metatarsal head, for which the cap will mate with the Morse taper interlock.
PLACEMENT OF FORMAL CAP COMPONENT
Confirm the trial size component so that it is congruent with the edge of the surrounding articular cartilage or slightly recessed.
Place the formal HemiCAP component to resurface the arthritic metatarsal head by tamping the cap into position as it forms a Morse taper interlock with the neck of the seated screw (TECH FIG 5).
TECH FIG 5 • A. The HemiCAP implant is placed in the suction delivery device. B. Formal HemiCAP implant is tamped into place, forming a Morse taper interlock with the previously seated screw.
BONE EXCISION AND MOTION ASSESSMENT
Remove dorsal osteophytes at this time with a microsagittal saw blade, osteotome, or rongeur. Any prominent bone along the dorsal, dorsomedial, and dorsolateral aspects is removed in an effort to eliminate any source of bony impingement as the hallux is brought into dorsiflexion (TECH FIG 6).
Assess dorsiflexion of the hallux with passive motion. If motion still appears restricted, where the hallux cannot be dorsiflexed to 70 degrees relative to long axis of the first metatarsal, then consider performing an additional soft tissue or bony procedure.
Consider a soft tissue procedure with release of plantar joint contracture (TECH FIG 7). This must be performed carefully so as not to cause any iatrogenic injury to the flexor hallucis brevis tendon or sesamoids. This may be performed with a Freer or McGlamry elevator or a small Beaver blade along the plantar capsule to elevate a few millimeters off the proximal phalangeal base or the plantar aspect of the first metatarsal.
After soft tissue release, perform a slow, gentle dorsiflexion stretch of the hallux in a controlled manner in an effort to stretch the joint contracture.
If after the soft tissue procedure more dorsiflexion is required, perform a simple Moberg closing wedge osteotomy of the proximal phalanx to improve dorsiflexion. Fixation of the Moberg phalangeal osteotomy may be achieved per the surgeon's preference. An Akin or biplanar (Mo-Akin) osteotomy may be performed in certain cases to address any concomitant mild hallux valgus (TECH FIG 8). Note: Avoid the Moberg procedure if there is no preoperative passive plantarflexion beyond neutral.
Obtain final AP and lateral fluoroscopic images to confirm alignment of the HemiCAP device (TECH FIG 9).
TECH FIG 6 • A. Excess bone along the dorsal, medial, and lateral aspects is removed with a microsagittal saw, osteotome, or rongeur, leaving an area of perimeter of bone to enclose the implant. B, C.Before and after decompression of surrounding bone around the HemiCAP.
TECH FIG 7 • Plantar soft tissue release is performed along with subchondral drilling of the dorsal area of proximal phalanx articular cartilage loss.
TECH FIG 8 • A. Moberg osteotomy is added by performing a dorsal closing wedge osteotomy of the proximal phalanx in certain cases for additional dorsiflexion. B. HemiCAP with Moberg osteotomy. C.Akin osteotomy or biplanar Mo-Akin osteotomy may be added at times to address concomitant mild hallux valgus.
TECH FIG 9 • AP and lateral radiographs after HemiCAP resurfacing.
POSTOPERATIVE CARE
A compressive dressing is placed intraoperatively.
The dressing is changed at 2 to 3 days postoperatively for a light dressing along the dorsal incision only with a waterproof Op-Site (FIG 7). This allows for less restriction due to the bandage and encourages early range of motion.
Early range-of-motion exercises are emphasized in an effort to preserve the motion gained intraoperatively. Some degree of motion loss is anticipated postoperatively from its intraoperative measurements, although every effort is made to minimize this amount.
We have found the first 2 to 3 weeks to be a critical period for maintaining motion. Swelling, hematoma, or hemarthrosis that occurs within the joint postoperatively contributes to the loss of motion seen after surgery. Recent attempts to minimize this with strict hemostasis and an early motion protocol are encouraged. Patients are instructed to begin toe motion
FIG 7 • The initial dressing is changed to a light dorsal postoperative dressing so as not to restrict early motion. A waterproof sealed Op-Site is used. exercises early at home several times per day, in addition to formal physical therapy. The only restriction is that no passive plantarflexion be performed beyond neutral for the first 4 weeks if a Moberg proximal phalangeal osteotomy was performed. Physical therapy and rehabilitation continue until the patient reaches a normal gait pattern and range of motion is maximized.
Patients are allowed to bear weight immediately on the heel of a rigid postoperative shoe or sandal. Between 3 and 4 weeks, the patient is transitioned to a running or jogging type of sneaker with a solid supportive sole.
Radiographs are obtained at 1 week, 6 weeks, and 12 weeks postoperatively. Subsequent radiographs are obtained at 6 months, 1 year, and 2 years postoperatively.
The patient should avoid placing high-impact stress on the joint, such as running, jogging, or sports involving pivoting and cutting, for at least the first 3 to 4 months postoperatively.
OUTCOMES
A study by Hasselman and Shields5 reported on 25 of their first 30 patients. At 20 months follow-up the patients showed a postoperative motion increase of 42 degrees (from 23 degrees preoperatively to 65 degrees postoperatively). Significant improvement in visual analog, AOFAS, and SF-36 scores were noted. All patients in this series claimed to be very satisfied with their results. Of note, an unspecified number of patients in this HemiCAP series underwent concomitant interpositional soft tissue grafting of the phalangeal side.
The results of our follow-up study13 on 36 patients at an average of 45 months were less favorable than those of the previously cited study, although fair satisfaction rates were achieved in this patient population that had refused to consider fusion. Good to excellent results were noted in 76% of patients, 12% fair, and 12% poor. We found a modest increase in dorsiflexion motion averaging 26 degrees (from 20 degrees preoperatively to 46 degrees postoperatively), along with improvement in visual analog scores from an average before surgery of 6.3 to an average of 2.2 after surgery. Although complete pain relief was not noted in most patients, the reduction of pain in the majority of the patients led to an overall satisfaction rate of 80% for the procedure at a follow-up of nearly 4 years. Intermediateterm radiographic evaluation of the HemiCAP prosthesis in 56 patients demonstrated no significant evidence of loosening; it appeared to show superior radiographic results compared to those of other metallic implants using a stemmed design.13
Occasional evidence of regrowth of bony osteophytes along the dorsal perimeter of the implant was noted, whereas several patients displayed some degree of progressive chondral surface loss on the apposing proximal phalangeal base. These two issues may be factors associated with significant persistent pain and less-than-satisfactory results.
When pain relief is the foremost goal of the patient, first MTP joint arthrodesis is the most predictable procedure for complete pain relief in advanced stages of hallux rigidus.
When pain relief and preservation of some degree of joint motion are the desired goals, metatarsal head HemiCAP resurfacing can provide a reduction in pain and satisfactory outcome when patients understand the modest expectations— namely that complete pain relief may not be achieved with this procedure, rather a reduction in pain and maintenance of motion.
FIG 8 • Second-generation HemiCAP design with dorsal flange.
It is critical to clearly explain this to the patient preoperatively so that the proper procedure can be chosen. As with all arthroplasty procedures (whether soft tissue interposition or implant), if the patient is unwilling to accept less-than-complete pain relief as a risk, then continued nonoperative treatment should be considered until a more predictable option becomes available or the patient accepts a fusion.
Unlike other metallic prosthetic implants or Silastic implants, the HemiCAP did not display evidence of loosening. Rather, the mode of failure in cases in which patients were not satisfied proved to be secondary to persistence of pain or lack of adequate pain relief. Reformation of dorsal osteophytes and crepitus of the joint around the prosthetic implant or progressive chondral wear of the apposing phalangeal base may account for the residual pain seen in some patients.
Given the lack of loosening seen in this implant, future design changes addressing dorsal periprosthetic bone formation and progressive arthritic changes of the proximal phalanx may provide a more predictable procedure with higher satisfaction rates. Design changes have been made for a second-generation HemiCAP with a dorsal flange and a more gradual dorsal curvature to the implant (FIG 8). These design modifications have been made in an effort to avoid recurrent periprosthetic dorsal osteophytes and improve the passive dorsiflexion gliding mechanism of the proximal phalanx on the metatarsal head during gait.
The lack of radiographic loosening is encouraging with this design, and it may serve as a model for future development. Design improvements are under way to address specific issues in an effort to improve the predictability of pain relief and satisfaction rates.
COMPLICATIONS
Joint stiffness
Periprosthetic dorsal osteophyte formation
Progressive arthritic changes, proximal phalangeal base
Sesamoiditis
Hallux valgus deformity
Lateral transfer metatarsalgia
Deep infection
Metallosis
REFERENCES
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· Easley ME, Davis WH, Anderson RB. Intermediate to long-term follow-up of medial-approach dorsal cheilectomy for hallux rigidus. Foot Ankle Int 1999;20:147–152.
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· Raikin SM, Ahmad J, Pour AE, et al. Comparison of arthrodesis and metallic hemiarthroplasty of the hallux metatarsophalangeal joint. J Bone Joint Surg Am 2007;89A:1979–1985.
· San Giovanni TP, Botto-Van Bemden A. First metatarsal head resurfacing: a new technique for surgical management of advanced hallux rigidus. Presented at American Academy of Orthopedic Surgery Annual Meeting, 2006.
· San Giovanni TP, Marx R, Botto-Van Bemden A, et al. Presented at American Orthopedic Foot and Ankle Society Specialty Day at American Academy of Orthopedic Surgeons Annual Meeting, May 2010, New Orleans, Louisiana.
· Seibert NR, Kadakia AR. Surgical management of hallux rigidus: cheilectomy and osteotomy phalanx and metatarsal. Foot Ankle Clin 2009;14:9–22.
· Thomas PJ, Smith RW. Proximal phalanx osteotomy for surgical treatment of hallux rigidus. Foot Ankle Int 1999;20:3–12.
· Townley CA, Taranow WS. A metallic hemiarthroplasty resurfacing prosthesis for the hallux metatarsophalangeal joint. Foot Ankle Int 1994;15:575–580.