Rice Body Formation Due to Different Etiologies in the Distal Forearm

Summary

The protocol describes the treatment of four rare cases of distal forearm synovitis with rice body formation from diverse etiologies (rheumatoid arthritis, trauma, and idiopathic) that were diagnosed by MRI and treated with surgical synovectomy and nerve release. No recurrence occurred postoperatively, underscoring surgery's efficacy in symptom resolution and prevention.

Abstract

Rice body formation in the distal forearm is an exceedingly rare clinical entity, often associated with chronic synovitis of varying etiologies. This study investigates four unique cases of forearm synovitis with rice body formation, hypothesizing that diverse underlying causes-rheumatoid arthritis, trauma, and idiopathic inflammation-contribute to this condition, and that surgical intervention ensures symptom resolution and prevents recurrence. The patients (three males, one female; aged 42-76 years) presented with heterogeneous clinical manifestations, including localized swelling, nerve compression symptoms, and restricted joint mobility. Diagnostic MRI revealed characteristic features: T1-weighted isointense masses with T2-weighted high-signal foci containing punctate low signals, aiding differentiation from other synovial pathologies. All patients underwent radical synovectomy with median nerve decompression, followed by histopathological analysis. Results demonstrated chronic granulomatous synovitis without evidence of infection (negative cultures and stains for tuberculosis, fungi, and bacteria). Postoperatively, all patients achieved complete symptom relief, with no recurrence or functional deficits observed during follow-up (9-22 months). Literature review highlighted the rarity of forearm rice bodies and underscored MRI's diagnostic superiority over radiography. The cases underscore that rice body formation, while historically linked to rheumatoid arthritis or tuberculosis, can arise from nonspecific synovial inflammation or trauma. Surgical excision combined with nerve release emerged as the definitive treatment, addressing both mechanical compression and inflammatory burden. This study emphasizes the importance of considering diverse etiologies in forearm synovitis, advocating for early MRI evaluation and tailored surgical management to optimize outcomes. The findings contribute to understanding the multifactorial pathogenesis of rice bodies and reinforce the efficacy of synovectomy in preventing recurrence and restoring function.

Introduction

Rice body is a kind of free particle with cartilaginous sheen, similar to the polished white rice, and was first reported by Reise in 1895 in a case of tuberculosis¹. It is mostly associated with rheumatoid diseases and tuberculosis^2,3, but it can also occur in trauma^4,5 or even in the absence of any clear cause^6,7. However, it is still very rare in the clinical practice of hand surgeons. Chronic nonspecific inflammation is thought to be associated with their formation, but the exact etiology and prognosis of rice bodies are still unknown.

Here we present four cases of rice body formation with chronic synovitis in the distal forearm, and a review of similar literature, focusing on the formation of rice body and discussing the diagnosis and treatment, with the aim of providing surgeons with ideas and theoretical bases for diagnosing and treating similar patients they encounter in clinical practice.

The rationale for developing and applying this technique arises from the diagnostic challenges and clinical consequences of rice body formation. Misdiagnosis or delayed diagnosis may prolong patient suffering, exacerbate nerve compression, and increase the risk of recurrence if incomplete excision is performed. By combining MRI-based early detection with definitive surgical excision and nerve release, this method addresses both the inflammatory burden and mechanical compression, thereby providing a comprehensive solution to optimize outcomes

The patients presented with localized swelling, nerve compression symptoms (e.g., numbness, positive Tinel's sign), and restricted joint mobility. Initial diagnostic tests included MRI, chosen for its superior soft-tissue resolution, which revealed characteristic rice body features: T1-weighted isointense masses with T2-weighted high-signal foci containing punctate low signals. These findings differentiated rice bodies from other synovial pathologies like pigmented villonodular synovitis (PVNS) or synovial osteochondromatosis, which exhibit distinct imaging patterns (e.g., hemosiderin deposition in PVNS or mineralization in osteochondromatosis). X-rays and CT scans were less sensitive but aided in assessing bony involvement and ruling out fractures. Laboratory tests-CRP, ESR, T-SPOT for tuberculosis, and bacterial/fungal cultures-were performed to exclude infectious or systemic inflammatory etiologies, all of which returned negative.

Compared with alternative imaging techniques such as radiography or CT, magnetic resonance imaging (MRI) provides superior soft-tissue resolution, enabling earlier and more accurate detection of rice bodies, as well as differentiation from mimicking conditions like pigmented villonodular synovitis (PVNS) and synovial osteochondromatosis^8,9. Previous studies have confirmed MRI's diagnostic superiority, as it identifies characteristic T1-isointense and T2-hypointense lesions with punctate hypointense foci, features that are often missed on X-rays or CT⁹. In terms of treatment, while arthroscopic debridement has been attempted, these methods are associated with incomplete clearance and higher recurrence rates¹⁰. In contrast, complete open synovectomy combined with nerve release has been consistently reported to achieve better symptom resolution, lower recurrence, and improved functional recovery. These advantages underscore why the present method is favored over less comprehensive alternatives.

The diagnosis of chronic synovitis with rice body formation was confirmed intraoperatively by histopathology, which demonstrated chronic granulomatous inflammation with lymphoplasmocytic infiltrates and necrosis, devoid of infectious agents or rheumatoid-specific features. Differential diagnoses considered included PVNS, synovial sarcoma, infectious tenosynovitis, and giant cell tumor of the tendon sheath, but MRI findings and histopathology excluded these.

The treatment plan involved radical synovectomy with median nerve decompression, aimed at removing inflammatory tissue, relieving nerve compression, and preventing recurrence. Surgical rationale centered on addressing mechanical compression (e.g., median nerve entrapment) and eliminating the inflammatory synovium responsible for rice body formation. Postoperatively, no recurrences or functional deficits were observed during follow-up (9-22 months), underscoring the efficacy of complete synovial excision. Potential complications, such as iatrogenic nerve injury, infection, or postoperative stiffness, were mitigated through meticulous surgical techniques and postoperative care. Long-term follow-up was emphasized to monitor for recurrence, particularly in idiopathic cases where the underlying etiology remained unclear. This approach highlights the importance of MRI in early diagnosis and tailored surgical intervention to optimize outcomes in this rare condition.

The primary goal of this method is to establish a standardized diagnostic and therapeutic approach that ensures early identification, accurate differentiation, and effective surgical management of rice body formation in the distal forearm. This method is most appropriate for clinicians managing patients with distal forearm swelling, nerve compression symptoms (such as numbness, tingling, or positive Tinel's sign), and restricted mobility where rice body formation is suspected. It is particularly valuable when initial radiographs or CT scans are inconclusive, but MRI demonstrates characteristic findings, and when laboratory studies exclude infectious causes such as tuberculosis or fungal tenosynovitis.

Protocol

The study protocols were approved by the Medical Ethics Committee of the First Affiliated Hospital of the College of Medicine, Zhejiang University. Written informed consent was obtained from the patients for publication of clinical details and clinical images.

1. Patient evaluation and initial assessment

1. Subject patients presenting with localized forearm swelling, numbness, restricted joint mobility, or positive Tinel's sign to a comprehensive clinical examination. Document symptoms suggestive of nerve compression or synovial pathology (e.g., progressive mass enlargement).
2. Obtain a detailed medical history, including prior trauma, rheumatoid arthritis, tuberculosis, or idiopathic inflammatory conditions. Medication use (e.g., immunosuppressants, corticosteroids) and record response to prior treatments.

2. Diagnostic imaging

1. Carry out a 3.0T MRI in a dedicated wrist coil with the forearm in neutral position. Carry out the following sequences: axial/coronal T1-weighted imaging (TR 500-700 ms, TE 10-20 ms, slice thickness 3 mm), fat-suppressed T2-weighted imaging (TR 3000-4000 ms, TE 50-80 ms). Key diagnostic criteria: rice bodies appear isointense to muscle on T1WI, hyperintense with punctate hypointense foci (salt-and-pepper sign) on T2WI, and demonstrate peripheral enhancement without central enhancement post-contrast. This protocol leveraged MRI's superior soft-tissue resolution to differentiate rice bodies from synovial osteochondromatosis or pigmented villonodular synovitis (PVNS).
2. Perform X-rays and CT scans to assess bony integrity, rule out fractures, or detect mineralization suggestive of alternative pathologies (e.g., synovial osteochondromatosis).

3. Laboratory testing

1. Carry out blood tests, including C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and rheumatoid factor (RF), to exclude systemic inflammation or autoimmune etiologies.
2. Perform T-SPOT testing, acid-fast staining, and fungal/bacterial cultures to rule out tuberculosis or infectious tenosynovitis.

4. Surgical intervention

1. Preoperative planning: Review MRI findings to delineate lesion margins and proximity to neurovascular structures. Map surgical access routes (e.g., longitudinal or S-shaped incisions) to minimize iatrogenic injury.
2. Perform all procedures under brachial plexus anesthesia with tourniquet control (250 mmHg) in a laminar-flow operating room. Prepare the surgical limb with sequential iodine-alcohol skin antisepsis 3x. Ask the surgical team to dress in full PPE (sterile gloves, fluid-resistant gowns, masks, and protective eyewear).
3. Administer a single preoperative 2 g intravenous cefazolin dose within 30 min prior to incision. Make a longitudinal/S-shaped incision along the volar forearm using a No. 15 scalpel blade, followed by sharp dissection through subcutaneous tissue with tissue scissors.
4. Using a No. 15 scalpel blade, an en bloc resection of the rice bodies together with the inflamed synovium was performed. Achieve hemostasis by bipolar cautery at 20 W setting (monopolar cautery avoided near nerves), and nerve decompression (if entrapped nerves) through longitudinal sharp dissection of the epineurium using microsurgical scissors - avoiding transverse traction to minimize postoperative scar constriction.
5. Rinse the wound surface with iodophor and clean water. After stopping the bleeding with an electric knife, perform layered suturing using 3-0 absorbable suture (Polyglactin). Apply 2 mL of sodium hyaluronate gel topically to reduce tendon adhesion. If tuberculosis or other communicable diseases cannot be ruled out, the surgical team wears N95 respirators, double gloves, and fluid-resistant aprons.
6. Send the synovial fragments and the contaminated liquid with blood for pathological examination, and then seal them in double-layer yellow medical waste bags¹¹.

5. Histopathological analysis

1. For resected specimens, carry out hematoxylin and eosin (H&E) staining to evaluate granulomatous inflammation, necrosis, and lymphoplasmocytic infiltrates.
2. Repeat with special stains (acid-fast, Grocott methenamine) and cultures on tissue samples to exclude occult infections.

6. Postoperative care

1. Avoid immediate postoperative immobilization to prevent tendon adhesion. Initiate early active mobilization protocols under physiotherapy guidance.
2. Administer analgesics (e.g., NSAIDs) and wound care to mitigate pain and infection risk.
3. The average hospital stay was approximately 1 week. Discharge patients once adequate pain control is achieved, the surgical wound is clean and stable, and early mobilization protocols can be initiated under outpatient supervision.

7. Follow up

1. Assess patients at 2 weeks, 3 months, and annually postoperatively. Carry out evaluations which include physical examination for recurrence, nerve function tests, and repeat MRI if symptoms recur.
2. Carry out long-term monitoring for early detection of recurrence, particularly in idiopathic cases, with a minimum follow-up duration of 12 months.

Results

Four cases were treated using the method described above. The details of all the cases and the outcome are described here.

Case 1

A 54-year-old woman presented to the hospital due to a 1-year history of a progressively enlarged mass in the distal left forearm. This mass was associated with numbness at the tip of the left fingers, but there were no sign...

Discussion

Rice bodies are generally considered to be fibrin complexes resulting from inflammatory processes in the joint, and usually present as progressively enlarged masses⁶. Several hypotheses have speculated on its formation, but there is no consensus on its etiology.

The earliest one was the synovial origin hypothesis. Cheung et al. postulated that rice bodies were triggered by the microinfarcts of synovial cells that resulted from inflammation and ischemia. Subsequently, in...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
3.0T MRI Scanner (Skyra)	Siemens Healthineers	Not specified
Acid-fast Stain Kit	Solarbio Life Sciences	G1170-50
bipolar electrotome	Wuhan Maolang Medical Technology Co., Ltd.	20162012293
Cefazolin (Injection, 2g)	Shijiazhuang No. 4 Pharmaceutical Co., Ltd.	H20054256
Grocott Methenamine Silver Stain Kit	Sigma-Aldrich	HT100A
Hematoxylin and Eosin Staining Kit	Beyotime Biotechnology	C0105S
Mayer’s Hematoxylin Stain Kit	Solarbio Life Sciences	G1120
PAS Stain Kit	Solarbio Life Sciences	G1281
Sodium Hyaluronate Gel (2ml)	Seikagaku Corporation Takahagi Plant	H20140533