Modified Oblique Keller Capsular Interposition Arthroplasty for Hallux Rigidus

Overview

Introduction

This paper describes the modified oblique Keller capsular interposition arthroplasty, which may be indicated for patients with late-stage hallux rigidus who wish to retain joint motion.

Step 1: Exposure

Make dorsal medial longitudinal incision over MTP joint and retract dorsal cutaneous nerve of great toe laterally.

Step 2: Mobilize Extensor Hallucis Longus Tendon

Separate extensor hallucis longus from dorsal aspect of capsule and extensor hallucis brevis and retract laterally.

Step 3: Mobilize Dorsal Aspect of Capsule and Extensor Hallucis Brevis Tendon

Leave inferior half of medial aspect of capsule attached to first metatarsal head to prevent late hallux valgus drift; make the capsular flap as long as possible.

Step 4: Perform Dorsal Cheilectomy and Resect Portion of Base of Proximal Phalanx to Decompress Joint

The greater the preoperative stiffness, the more bone needs to be removed from the phalanx base.

Step 5: Interpose Capsule and Suture Capsule to MTP Plantar Plate

Advance the dorsal aspect of the capsule over the metatarsal head and suture it into the plantar plate with absorbable suture in an interrupted fashion.

Step 6: Imbricate Medial Aspect of Capsule

Imbricate the medial aspect of the capsule with absorbable suture to hold the toe in a corrected position.

Step 7: Close Wound and Apply Supportive Dressing

Perform layered closure and apply forefoot compression dressing.

Step 8: Postoperative Care

Patient performs active range-of-motion exercises of great-toe MTP and IP joints, intrinsic muscle strengthening, and scar massage.

Results

We compared a cohort of patients who had the modified oblique Keller capsular interposition arthroplasty (MOKCIA) with a group who had an arthrodesis of the first MTP joint.

What to Watch For

Indications

Contraindications

Pitfalls & Challenges

Introduction

This paper describes the modified oblique Keller capsular interposition arthroplasty, which may be indicated for patients with late-stage hallux rigidus who wish to retain joint motion.

Hallux rigidus is a common disorder of the foot characterized by pain at the first metatarsophalangeal (MTP) joint and limited hallux motion due to localized osteoarthritis at the first MTP joint. Patients with unsuccessful conservative treatment can be managed with one of several operative procedures. In cases of advanced osteoarthritis with pain throughout MTP joint motion, the joint is not salvageable. In these cases, arthrodesis (fusion), implant arthroplasty, or interpositional/resection arthroplasty are options. Arthrodesis is associated with malunion, nonunion, ray shortening, and transfer metatarsalgia¹. Successful fusion eliminates pain but sacrifices mobility, and the concept of eliminating motion at the MTP joint is not easily accepted by many patients. Implant arthroplasty with silicone or high-density polyethylene/metal composites is associated with stiffness, wear-debris synovitis, and high failure rates^2,3.

The Keller resection arthroplasty maintains some MTP joint motion. It was initially described for correction of hallux valgus deformity⁴ and involved resection of a substantial portion (up to one-third) of the proximal portion of the proximal phalanx, resulting in a high rate of complications including lateral transfer metatarsalgia, decreased great-toe strength, excessive shortening of the first ray, cock-up deformity, and clawing of the interphalangeal (IP) joint^5,6. Modified versions of the resection arthroplasty have been introduced for the treatment of hallux rigidus in an attempt to reduce these complications, maintain hallux MTP joint motion, and provide more predictable pain relief. Hamilton et al.⁷ modified the Keller procedure to reduce the amount of proximal phalanx bone removed to include only the proximal one-fourth of the phalanx and interposed the dorsal aspect of the MTP joint capsule into the joint to act as a tissue spacer between the ends of the bone in the decompressed MTP joint space. Mroczek and Miller⁸ further modified Hamilton's procedure by changing the obliquity of the proximal phalanx bone resection to retain the plantar base of the proximal phalanx and thereby the sesamoid ligament insertion. The modified oblique Keller capsular interposition arthroplasty (MOKCIA) is a motion-preserving procedure that is appealing to younger or more active patients, those with adjacent arthritis, and those who do not desire a fusion.

Patients are considered candidates for the MOKCIA procedure if they have late-stage hallux rigidus and desire a procedure that preserves joint motion. Ideal candidates do not have deformity such as hallux valgus and have had unsuccessful nonoperative conservative treatment, which may include a foot orthosis with a turf toe plate, activity modification, anti-inflammatory medications, and injections of corticosteroids.

The procedure involves eight steps.

Step 1: Exposure

Step 2: Mobilize extensor hallucis longus tendon

Step 3: Mobilize dorsal aspect of capsule and extensor hallucis brevis tendon

Step 4: Perform dorsal cheilectomy and resect portion of base of proximal phalanx to decompress joint

Step 5: Interpose capsule and suture capsule to MTP plantar plate

Step 6: Imbricate medial aspect of capsule

Step 7: Close wound and apply supportive dressing

Step 8: Postoperative care

Step 1: Exposure

Make dorsal medial longitudinal incision over MTP joint and retract dorsal cutaneous nerve of great toe laterally.

• With the patient positioned supine, apply a nonsterile ankle Esmarch or thigh tourniquet. Either an ankle block with heavy sedation or general anesthesia with a laryngeal mask airway is sufficient for anesthesia. Administer prophylactic intravenous antibiotics prior to the tourniquet inflation and incision.

• After sterile preparation and draping, make a dorsal medial longitudinal incision over the MTP joint. Identify, protect, and gently retract the dorsal cutaneous nerve of the great toe laterally.

Step 2: Mobilize Extensor Hallucis Longus Tendon

Separate extensor hallucis longus from dorsal aspect of capsule and extensor hallucis brevis and retract laterally.

Dissect along the interval between the extensor hallucis longus and the extensor hallucis brevis tendons and elevate the extensor hallucis longus away from these underlying structures. Retract the extensor hallucis longus tendon laterally to avoid cuttting it during Step 3.

Step 3: Mobilize Dorsal Aspect of Capsule and Extensor Hallucis Brevis Tendon

Leave inferior half of medial aspect of capsule attached to first metatarsal head to prevent late hallux valgus drift; make capsular flap as long as possible.

• Perform a medial longitudinal capsulotomy to provide access to the joint by subperiosteal dissection. Dissect subperiosteally over the dorsal aspect of the first metatarsal head. Leave the inferior half of the medial aspect of the capsule attached to the first metatarsal head to prevent late hallux valgus drift. If there is an associated prominence of the medial eminence requiring complete stripping of the medial aspect of the first metatarsal head, repair the capsule at the time of closure.

• Remove the attachments of the dorsal aspect of the capsule and the short extensor to the great toe from along the dorsal ridge of the base of the proximal phalanx.

Step 4: Perform Dorsal Cheilectomy and Resect Portion of Base of Proximal Phalanx to Decompress Joint

The greater the preoperative stiffness, the more bone needs to be removed from the phalanx base.

• Using a sagittal saw, remove the dorsal one-third of the metatarsal head with associated osteophytes (Fig. 1).

• Make an oblique osteotomy from medial to lateral to remove a wedge-shaped portion of the base of the proximal phalanx, removing more bone dorsally to preserve the insertion of the short flexors on the plantar base of the proximal phalanx. The amount of bone removed from the phalanx depends on the preoperative stiffness. The greater the preoperative stiffness, the more bone needs to be removed from the phalanx base.

• Create a joint space of at least 5 mm to allow adequate room for interposition of the capsule.

• Evaluate intraoperative motion to ensure that there is at least 80° of dorsiflexion relative to the first metatarsal shaft prior to capsular interposition.

Fig. 1.

Bone resection performed to decompress the first MTP joint. Care is taken to avoid excessive dorsal cheilectomy that may destabilize the MTP joint.

Step 5: Interpose Capsule and Suture Capsule to MTP Plantar Plate

• Advance the dorsal aspect of the capsule over the metatarsal head and suture it into the plantar plate with absorbable suture in an interrupted fashion (Figs. 2 and 3). This technique requires manual distraction of the joint and a small curved needle for the intracapsular suture.

• Place three or four sutures into the plantar plate; then have an assistant hold the distal end of the capsular flap against the plantar plate while all of the sutures are tied. Place a traction suture into the distal end of the capsule and pass it through the plantar plate and out of the skin on the plantar aspect of the MTP joint to aid in placement of the capsule deep into the joint as the sutures are tied. Then remove the traction suture.

• Release the extensor hallucis brevis tendon with a tenotomy as proximal as possible to allow complete excursion of the dorsal aspect of the capsule over the metatarsal head deep into the space (Fig. 4). This technique is aided by manual distraction of the joint and a small 1/2 curved tapered needle for the intracapsular suture (UCL needle, Cat. No. Z114 absorbable or X114 nonabsorbable; Ethicon, Somerville, New Jersey).

Fig. 2.

The dorsal aspect of the capsule is shown dissected off the MTP joint in preparation for suturing over the metatarsal head into the plantar plate.

Fig. 3.

The dorsal aspect of the capsule draped over metatarsal head and interposed between the joint surfaces.

Fig. 4.

The dorsal aspect of the capsule has been sutured to the plantar plate, and the medial aspect of the capsule has been repaired. Note the tendon of the extensor hallucis brevis on the dorsal aspect of the capsule; the tendon has been released proximally to allow full distal excursion of the capsule in order to provide full coverage over the metatarsal head.

Step 6: Imbricate Medial Aspect of Capsule

• Imbricate the medial aspect of the capsule with absorbable suture to hold the toe in a corrected position.

• Use intraoperative fluoroscopy to determine the degree of osseous resection as well as alignment (Figs. 5-A and 5-B). Figures 6-A and 6-B graphically depict the osseous decompression, which is done while preserving the insertion of the flexor hallux brevis tendon on the base of the proximal phalanx. Figure 6-B shows the extensor hallucis brevis tenotomy and excursion of the dorsal aspect of the capsule into the space created.

Fig. 5-A Fig. 5-B.

Intraoperative anteroposterior and lateral fluoroscopic views demonstrating the extent and obliquity of the ostectomy of the base of the phalanx and metatarsal head.

Fig. 6-A.

The amount of osseous resection performed while preserving the insertion of the short flexors on the base of the proximal phalanx.

Fig. 6-B.

The extensor tenotomy and excursion of the dorsal aspect of the capsule into the joint.

Step 7: Close Wound and Apply Supportive Dressing

Perform layered closure and apply forefoot compression dressing.

• Irrigate the wound and close the skin with a layered closure, using 3-0 Monocryl (poliglecaprone; Ethicon) suture in subcutaneous skin and 3-0 nylon vertical mattress sutures to close the skin.

• Place a forefoot compression dressing using gauze wrap and a Coban wrap to support the toe in a neutral position.

Step 8: Postoperative Care

Patient performs active range-of-motion exercises of great-toe MTP and IP joints, intrinsic muscle strengthening, and scar massage.

• A postoperative shoe is provided to the patient, who is allowed to walk bearing weight through the heel as tolerated immediately postoperatively.

• At ten to fourteen days, remove the skin sutures and wrap the foot with a 3-in (7.6-cm) Ace wrap for swelling control and to support the toe. Instruct the patient to remove the Ace wrap several times per day and do passive and active range-of-motion exercises of the great-toe MTP and IP joints, intrinsic muscle strengthening, and scar massage.

• Wean the patient from the postoperative shoe to an athletic shoe at four weeks postoperatively.

• Establish routine visits at two weeks, four weeks, and ten to twelve weeks postoperatively.

Results

We compared a cohort of patients who had the modified oblique Keller capsular interposition arthroplasty (MOKCIA) with a group who had an arthrodesis of the first metatarsophalangeal (MTP) joint⁹. We evaluated ten toes in ten patients at an average of sixty-three months (range, twenty-three to 101 months) after the MOKCIA and twelve toes in twelve patients at an average of sixty-eight months (range, twenty-seven to ninety-six months) after the MTP joint arthrodesis. Clinical outcomes were evaluated with the American Orthopaedic Foot & Ankle Society (AOFAS) clinical rating system for the hallux and the Foot and Ankle Ability Measure (FAAM). Range-of-motion measurements, dynamometer strength testing, plantar pressure testing, and radiographic studies also were performed.

The AOFAS score for the MOKCIA group was significantly higher than that for the arthrodesis group. The MOKCIA group exhibited passive (54°) and active (30°) ranges of motion of the MTP joint. As compared with the MOKCIA group, the arthrodesis group had significantly higher plantar pressures under the great toe but not under the second or third metatarsal head.

This evidence suggests that the MOKCIA is a motion-sparing procedure with clinical outcomes equivalent to those of arthrodesis and that it results in a more normal pattern of plantar pressures during walking.

What to Watch For

Indications

• The modified oblique Keller capsular interposition arthroplasty (MOKCIA) is a motion-preserving procedure that is appealing to younger or more active patients, those with adjacent arthritis, and those who do not desire a fusion.

• Patients are considered a candidate for the MOKCIA procedure if they have late-stage hallux rigidus and desire a procedure that preserves MTP joint motion.

• Patients must first have had unsuccessful nonoperative treatment such as orthotics and a turf toe plate, activity modification, anti-inflammatory medications, and injections of corticosteroids.

• Pain should be throughout the entire MTP joint range of motion rather than isolated to dorsiflexion.

Contraindications

• The MOKCIA will not correct deformity and is contraindicated in cases of hallux valgus with secondary arthritis.

• Early-stage degenerative changes with pain isolated to MTP joint dorsiflexion only. Patients with those findings are potentially good candidates for cheilectomy alone.

• Patients with substantial stiffness and postoperative scarring around the MTP joint.

• A short first ray because there is a concern about transfer metatarsalgia.

Pitfalls & Challenges

• Failure to release the proximal part of the extensor hallucis brevis tendon will make capsular excursion more difficult.

• The procedure is not indicated for the correction of hallux valgus.

• The medial capsular imbrication corrects residual valgus after the reconstruction is complete and helps prevent valgus drift of the toe postoperatively.

Clinical Comments

• Would patients who found relief after the MOKCIA have benefited from isolated dorsal cheilectomy?

  One of us (J.E.J.) believes that dorsal cheilectomy is indicated if the pain is only at the end ranges of motion. If a patient also has pain throughout the midrange of motion, then cheilectomy alone is not indicated and MOKCIA or fusion is a better option.

• When do you consider a dorsal cheilectomy a valid option when patients have radiographic evidence of advanced osteoarthritis?

  When patients have radiographic evidence of advanced arthritis, we believe that an isolated dorsal cheilectomy would be indicated only if there was a functional range of motion of >30° of dorsiflexion and pain was only at the end ranges of motions.