DJD & Hallux Rigidus - Foot & Ankle

Introduction

A condition characterized by loss of motion of first MTP joint in adults due to degenerative arthritis
- osteophyte formation leads to dorsal impingement
Pathoanatomy
- primary etiology unknown
- acute trauma and repetitive microtrauma predispose to arthritic changes
- anatomic variations of first metatarsal may play a role in arthritic predisposition

Classification

Coughlin and Shurnas Classification
	Exam Findings	Radiographic Findings
Grade 0	Stiffness	Normal
Grade 1	mild pain at extremes of motion	mild dorsal osteophyte, normal joint space
Grade 2	moderate pain with range of motion increasingly more constant	moderate dorsal osteophyte, <50% joint space narrowing
Grade 3	significant stiffness, pain at extreme ROM, no pain at mid-range	severe dorsal osteophyte, >50% joint space narrowing
Grade 4	significant stiffness, pain at extreme ROM, pain at mid-range of motion	same as grade III

Presentation

Symptoms
- first ray and 1st MTP pain and swelling worse with push off or forced dorsiflexion of great toe
- shoe irritation due to dorsal osteophytes and compression of dorsal cutaneous nerve may lead to paresthesias
- pain becomes less severe as the disease progresses
- transfer metatarsalgia
Physical exam
- limited dorsiflexion
- pain with grind test
- inverted gait
- decreased push-off strength

Imaging

Radiographs
- recommended views
  - AP, lateral, and oblique views
- findings
  - osteophytes, especially dorsal
  - joint space narrowing
  - subchondral sclerosis and cysts

Treatment

Nonoperative
- NSAIDS, activity modification & orthotics
  - indications
    - grade 0 and 1 disease
  - activity modifications
    - avoid activities that lead to excessive great toe dorsiflexion
  - types of orthotics
    - Morton's extension with stiff foot plate is the mainstay of treatment
    - stiff sole shoe and shoe box stretching may also be used
Operative
- joint debridement and synovectomy
  - indications
    - patients with acute osteochondral or chondral defects
- dorsal cheilectomy
  - indications
    - grade 1 and 2 disease
    - select patients with grade 3 disease may benefit from cheilectomy
    - pain with terminal dorsiflexion is an indicator of good results with dorsal cheilectomy
    - shoe wear irritation from dorsal prominence and pain (ideal candidate)
    - contraindicated when pain located in the mid-range of the joint during passive motion
  - technique
    - remove 25-30% of the dorsal aspect of the metatarsal head along with dorsal osteophyte resection
    - the goal of surgery is to obtain 70-90% of dorsiflexion intraoperatively
- Moberg procedure (dorsal closing wedge osteotomy of the proximal phalanx)
  - indications
    - runners with reduced dorsiflexion (60° is needed to run)
    - failure of cheilectomy to provide at least 30 to 40 degrees of motion
  - technique
    - increases dorsiflexion by decreasing the plantar flexion arc of motion
- Keller Procedure (resection arthroplasty)
  - indications
    - elderly, low demand patients with significant joint degeneration and loss of motion
    - contraindicated in patients with pre-existing rigid hyperextension deformity of 1st MTP joint
  - technique
    - involves removing the base of the first proximal phalanx
    - risk of hyperextension (cock-up deformity), weakness with push-off, and transfer metatarsalgia (decreased with capsular interposition)
- MTP arthroplasty
  - indications
    - indications controversial
  - technique
    - capsular interpositonal arthroplasty gaining popularity
    - silicone implants are not recommended due to poor long-term results
  - outcomes
    - silicone implants may have a good short term satisfaction rate
    - osteolysis and synovitis cause mid to long term pain and joint destruction
- MTP joint arthrodesis
  - indications
    - grade 3 and 4 disease (significant joint arthritis)
    - most common procedure for hallux rigidus
  - outcomes
    - 70% to 100% fusion rate
    - 15% of patients experience degeneration of IP joint after surgery (mostly asymptomatic)
- MTP joint arthrodesis with structural bone graft
  - indications for structural bone graft
    - 1st MT shortening that cannot be adequately rebalanced with a lesser metatarsal osteotomy (usually shortening > 5 mm)
      - most commonly seen with failed MTP arthroplasty
    - significant proximal phalanx bone loss with inadequate remaining bone for fixation without compromising IP joint,
    - 1st MT shortening with loss of medial support of the 2nd toe predisposing to varus at the 2nd MTP joint.

Techniques

MTP joint arthrodesis
- dorsal plate with compression screw is biomechanically strongest construct
- preferred surgical alignment
  - 10 to 15 degrees of valgus in relation to the metatarsal shaft
  - 15 degrees of dorsiflexion in relation to the floor
  - Best way to assess this introperatively is with foot plate to simulate weight bearing with 4-8mm of clearance of toe from plate
- fusion in excessive dorsiflexion causes pain at tip of the toe, over the IP joint, and under the 1st metatarsal with excessive dorsiflexion
- fusion in excessive plantar flexion causes increased pressure at the tip of the toe
- fusion in excessive valgus increases the risk of IP joint degeneration

Complications

Failed arthroplasty
- treatment
  - implant resection, synovectomy if there is isolated great toe pain
  - implant resection, bone grafting, and arthrodesis if there is great toe pain with lesser toe metatarsalgia
Nonunion
- uncommon following 1st MTP arthodesis, union rate is 90+%
- 32% of patients with a nonunion are asymptomatic
- treatment
  - revision with bone grafting