What is the diagnosis and treatment for a patient with pain in the left foot and X-ray findings showing moderate degenerative changes at the 1st Tarsometatarsal (TMT) joint and a moderate-sized plantar calcaneal enthesophyte?

Diagnosis and Treatment of Left Foot Pain with 1st TMT Joint Degenerative Changes and Plantar Calcaneal Enthesophyte

Diagnosis

This patient has two distinct pathologies: (1) osteoarthritis of the first tarsometatarsal (TMT) joint and (2) plantar calcaneal enthesophyte (heel spur), both of which are contributing to the foot pain. 1, 2

First TMT Joint Degenerative Changes

• The moderate degenerative changes at the 1st TMT joint represent osteoarthritis, which causes midfoot instability and pain 3
• This condition commonly results from post-traumatic injury (even if remote or unrecognized), chronic instability, or degenerative processes 3
• The 1st TMT joint is critical for midfoot integrity, and arthritis here significantly impacts foot biomechanics and weight-bearing 3

Plantar Calcaneal Enthesophyte

• The moderate-sized plantar calcaneal enthesophyte is a bony outgrowth at the calcaneal insertion sites, most commonly arising from the abductor digiti minimi and flexor digitorum brevis muscles (50% of cases each), or between the plantar fascia and these muscles 4
• Only 3% of enthesophytes actually arise within the plantar fascia itself 4
• This finding is often associated with plantar fasciitis, though the enthesophyte itself may or may not be the primary pain generator 2

Additional Diagnostic Workup Needed

MRI of the left foot without IV contrast is the most appropriate next imaging study to fully characterize both pathologies and guide treatment planning. 1, 2

Specific MRI Evaluation Points

• For the 1st TMT joint: Assess cartilage loss severity, subchondral bone changes, synovitis, and joint instability 1
• For heel pain: Evaluate plantar fascia thickness (>4mm is abnormal), focal echogenicity changes, perifascial edema, and exclude plantar fascia tear 2
• Rule out other pathologies: Exclude Baxter's neuropathy (inferior calcaneal nerve compression), tarsal tunnel syndrome, calcaneal stress fracture, and occult fractures 1, 2

Alternative Imaging if MRI Unavailable

• Ultrasound can assess plantar fascia pathology with 80% sensitivity and 88% specificity (95% sensitivity with elastography) and allows dynamic examination 2
• Weight-bearing radiographs have already been obtained and show the degenerative changes; CT may add value for surgical planning of the TMT joint but is not essential initially 1

Treatment Algorithm

Conservative Management (First-Line for Both Conditions)

Initial conservative treatment should be attempted for 3-6 months before considering surgical intervention, unless there is severe instability or disability. 2, 3

For 1st TMT Joint Arthritis:

• Orthotic support: Custom orthotics with rigid arch support to stabilize the midfoot and reduce motion at the arthritic joint 3
• Footwear modification: Stiff-soled shoes or rocker-bottom shoes to limit TMT joint motion during gait 3
• NSAIDs: For pain and inflammation control (if no contraindications)
• Activity modification: Avoid high-impact activities and prolonged weight-bearing 3

For Plantar Calcaneal Enthesophyte/Plantar Fasciitis:

• Stretching exercises: Plantar fascia and Achilles tendon stretching 2
• Orthotic devices: Heel cups, cushioned insoles, or custom orthotics with arch support 2
• Night splints: To maintain ankle dorsiflexion and stretch the plantar fascia 2
• Physical therapy: Including ultrasound therapy and strengthening exercises 2
• NSAIDs: For pain control 2

Surgical Management (If Conservative Treatment Fails)

For 1st TMT Joint Arthritis:

Arthrodesis (fusion) of the first TMT joint is the definitive surgical treatment for symptomatic arthritis that has failed conservative management. 3, 5

• Surgical technique: Fusion using compression screw and plantar interlocking plate has significantly lower rates of nonunion and soft tissue complications compared to dorsal or medial plate positioning 5
• Advantages of plantar plating: Better biomechanical stability and good soft tissue coverage by the abductor hallucis muscle 5
• Post-operative protocol:
  • Long sole post-operative shoe with weight-bearing as tolerated for 6 weeks 5
  • Full weight-bearing at 6-8 weeks when radiographic healing is confirmed 5
  • No high-demand sports for 12 weeks 5

For Plantar Calcaneal Enthesophyte:

• Surgical excision of the enthesophyte and release of the plantar fascia is reserved for cases refractory to at least 6 months of conservative treatment 2
• The enthesophyte itself is often not the primary pain source, so surgery should focus on addressing underlying plantar fascia pathology 4

Critical Clinical Pearls

• Do not assume the enthesophyte is causing the heel pain: Only 3% of plantar enthesophytes arise within the plantar fascia; most arise from muscle insertions and may be incidental findings 4
• The 1st TMT joint arthritis will not improve with conservative treatment alone: While symptoms may be managed, the degenerative process is irreversible, and arthrodesis provides definitive treatment 3, 5
• Obtain MRI before committing to surgery: This ensures no occult pathology is missed and allows proper surgical planning 1, 2
• Weight-bearing radiographs are essential: Non-weight-bearing films may underestimate the degree of TMT joint instability and malalignment 2