54-year-old female stumbled whilst on holiday in March 2020 with persistent swelling, severe pain and unable to wear proper shoes. Further imaging was performed on the basis of GP request.
Radiographic findings were described as:
The patient continued to experience pain and swelling. Hence, MRI to rule out infection or injury to ligament or tendon was performed.
MRI has shown:
The appearances were of motion-related marrow oedema than infection.
The patient was managed conservatively with anti-inflammatory medications and physiotherapy.
Background
First metatarsophalangeal joint (MTPJ)osteoarthritis, otherwise known as hallux rigidus in orthopaedic communities, is an incredibly common degenerative condition characterised by forefoot pain, motion restriction and functional interference of MTPJ. It is the common endpoint of degenerative, long-standing trauma such as turf toe, crystalline or inflammatory arthropathy. Commonly affecting those more than 50 years of age, it is often bilateral and shows female predilection [1].
Clinical Perspective
Its treatment options include conservative measures like anti-inflammatory medications, shoe modification, physiotherapy and surgical options, until 2016, include cheilectomy, soft tissue interposition or resection arthroplasty, partial or total arthroplasty or arthrodesis, providing a variable degree of pain relief to patients. MTPJ arthrodesis, although considered gold-standard and provides excellent pain relief, sacrifices joint motion and function. Hence, foot and ankle surgeons explore more function-preserving treatment options, including novel hydrogel or more physiological synthetic cartilage implantation hemiarthroplasty [2,3].
Foot surgeons rely heavily upon imaging for preoperative planning and postoperative assessment. Radiographs and MRI can detect osteoarthritis severity by depicting joint space loss, osteophytes, subchondral changes and valuable information about bone quality and adjacent soft tissue amenable for reconstruction preoperatively [4]. Following MTPJ procedure, radiographs are used to identify the degree of fusion, metalwork fracture or loosening following arthrodesis, implant loosening or periprosthetic fracture following arthroplasty.
Imaging Perspective and outcome
Following implantation hemiarthroplasty, normal radiographic appearances include well-defined radiolucency reaching the first MTPJ with an absent central metatarsal head, thin sclerotic margin, narrow transition zone with adjacent normal bone, lack of periosteal reaction and restoration of joint space (up to 3 mm). On MRI, in the axial plane, the implant is seen as iso to hyperintense featureless square area in the metatarsal head on T1-weighted image which is remarkably hypointense on STIR or T2-weighted fat-suppressed images. Coronal images show circular area embedded in the centre of the metatarsal head. Typically, there should be no fluid or marginal irregularity around implant, synovitis or diffuse adjacent soft tissue oedema. The implant should be proud of the metatarsal head cortex between 1.5 to 3 mm [5].
In addition to implant loosening, wear, infection, reactive aseptic synovitis common to hemiarthroplasties at all anatomical sites, first MTPJ implantation hemiarthroplasty-specific complications include proximal phalanx intraosseous cystic changes, cortical rim fracture at the metatarsal head, the recession of the implant into the metatarsal shaft or too proud (>3 mm) implant. If hemiarthroplasty fails, the MTPJ arthrodesis is the preferred surgical option [3,5].
Take-Home Message / Teaching Points
Polyvinyl alcohol implantation MTPJ hemiarthroplasty masquerading as old osteomyelitis
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The patient is a 54-year-old female with persistent swelling and severe pain in the great toe metatarsophalangeal joint (i.e., the first MTP joint), making it difficult to wear shoes normally. X-ray images show partial loss of the joint space in the first MTP joint, with subchondral sclerosis, osteophytes, and changes in the joint margins. Some images demonstrate a square-shaped lucent area in the central portion of the first metatarsal head, with a clearly delineated interface between it and the surrounding bone cortex, showing no obvious destruction or abnormal periosteal reaction. The joint space appears to have partially recovered compared to the original state, suggesting the presence of an implant.
MRI reveals a square-shaped, near-isointensity signal in the center of the metatarsal head on T1-weighted images, with markedly reduced signal on T2/STIR sequences. There is no significant edema or inflammatory signal in the surrounding soft tissue. This finding is consistent with the imaging characteristics of a hydrogel (polyvinyl alcohol-saline) prosthesis within the joint, and there are no obvious signs of joint effusion, synovial thickening, or periprosthetic infection.
Combining the patient's age, clinical symptoms, imaging features (especially the square-shaped hydrogel implant on MRI with clear boundaries and no significant soft tissue reaction), and a history of foot trauma/surgery, the most likely diagnosis is:
First metatarsophalangeal joint osteoarthritis treated with hydrogel implant arthroplasty. Current imaging findings indicate stable positioning of the implant and the surrounding bone, with no obvious complications.
If the patient’s pain is notably relieved and joint function remains adequate, the following comprehensive management strategies may be employed:
This report is based on the currently provided medical history and imaging data for reference purposes only and cannot replace an in-person clinical diagnosis or treatment advice from a professional physician. If symptoms persist or worsen, please seek immediate medical attention and undergo further relevant examinations.
Polyvinyl alcohol implantation MTPJ hemiarthroplasty masquerading as old osteomyelitis
