Neuropathic Bone Disease PDF

Neuropathic Bone Disease Allen J Kempf, DPM, MS, FACFAS Assistant Professor College of Podiatric Medicine and Surgery Des Moines University Objectives Demonstrate knowledge of the etiology and pathophysiology of neuropathic bone disease Demonstrate knowledge of diagnostic testing and...

Neuropathic Bone Disease Allen J Kempf, DPM, MS, FACFAS Assistant Professor College of Podiatric Medicine and Surgery Des Moines University Objectives Demonstrate knowledge of the etiology and pathophysiology of neuropathic bone disease Demonstrate knowledge of diagnostic testing and diagnostic features of neuropathic bone disease Identify treatment options for neuropathic bone disease  Definition “Charcot foot is a progressive condition characterized by joint dislocation, pathological fractures, and severe destruction of the pedal architecture.” JFAS, Supplement 2000, Diabetic Foot Disorders: A Clinical Practice Guideline, p S39 6 D’s Destruction Debris Dislocation Distention Disorganization Increased Density (subchondral sclerosis) Etiologies Diabetes Spinal Disorders – Most common MS Tabes dorsalis CMT Leprosy Paraneoplasms Syringomyelia Transplant Steroids – Kidney – 20% Alcoholism – Kidney-pancreas Pernicious anemia – 31% Statistics Prevalence of Charcot neuroarthropathy – 0.1-7.5% reported in general diabetic patient population – Up to 35% in diabetic patients with neuropathy – Patients typically have DM for 10 years or more prior to onset – Reported bilateral occurrence between 9 and 75% – Mean age is 50.3 years Pathophysiology Neurotraumatic theory – Exaggerated overuse injury coupled with loss of protective sensation – Can be initiated by acute trauma or repetitive microtrauma – Lack of sensation allows continued tissue destruction resulting in fractures and dislocations Pathophysiology Neurovascular theory – Vasomotor neuropathy in patients with intact blood flow – Arteriovenous shunting leads to excessive bone resorption and bone weakening – Contributes to fractures and dislocations with continued weightbearing  Pathophysiology Increased inflammatory response in the foot Osteoclast – Osteoblast imbalance with increased osteoclasts present Increase in osteoclasts cause lysis of bone leading to more inflammation Leads to bone and joint destruction https://www.sciencephoto.com/media/74491/view/osteoclasts-in-bone-lacunae-sem Pathophysiology – RANK L https://www.researchgate.net/figure/The-role-of-RANKL-in-Charcot-neuroarthropathy_fig1_221683592 Pathophysiology Histology – Bone and cartilage debris embedded in synovium – Replacement of cartilage by fibro-osseous tissue https://www.researchgate.net/figure/Histology-Slides-demonstrating-histologic-changes-seen-in-patient-with-Charcot_fig3_286764865 Risk Factors Trepman, E, FAI. 2005.  Eichenholtz Classification Trepman, E, FAI. 2005. Eichenholtz Stage I Eichenholtz Stage II Eichenholtz Stage III Brodsky Classification 20% 10% 60 % Clinical features Red, hot, swollen foot Temperature difference – >2 degrees Celsius Usually, a sensory neuropathy present Some pain may be present, but does not match amount of destruction Bilateral 9-30% of the time Differential Diagnosis Charcot arthropathy can mimic many conditions Infection Rheumatoid arthritis Osteoarthritis Gout Osteomyelitis Diagnosis Based on clinical features – Red, hot (temp >2 degrees Celsius compared to contralateral limb), edematous – Radiographic findings – Cortical fractures, periosteal reaction, joint debris, deformity, dislocation, rocker-bottom deformity – Lack of break in skin  Osteomyelitis or Charcot? Presence of ulcer can complicate diagnosis – Xray findings will be similar for both – May need further imaging – Bone scans, MRI – Bone biopsy “gold standard” https://www.tsc-deutschland.de/wp-content/uploads/2017/08/2012-eng-bd-jamshidi.pdf  osteo Charcot Nuclear medicine Three phase Te99-MDP bone scan has an 85% sensitivity, but a 55% specificity because of other causes of bone remodeling Ga67 has high false-positive rate In111 has highest sensitivity (87%) and specificity (81%) in detecting osteo in a neuropathic foot Nuclear Medicine Best approach is to do a combined scan Te99-MDP and Te99-HMPAO (Ceretec) scan is 94% sensitive and 91% specific Te99-MDP and In111 scan is 86% sensitive and 94% specific Te99-Sulfur Colloid and In111 more recently has also been shown to be effective  Nuclear Medicine (+) Te99- (+) WBC scan Osteomyelitis MDP (+) Te99- (-) WBC scan Charcot MDP (-) Te99-MDP (+) WBC scan Soft tissue infection (cellulitis) (-) Te99-MDP (-) WBC scan No osteo or active Charcot  MRI: Charcot and OM T1 images show decreased signal intensity T2 images show increased signal intensity STIR images show high signal marrow edema MRI Bone marrow edema may be present with both Charcot and OM Bone marrow edema near ulcer, or revealing sinus tracts, suspicious of bone infection Charcot edema present in peri-articular fashion Probing to Bone Being able to probe to bone with a metallic instrument had a positive predictive value of 89% for diagnosing osteomyelitis Grayson ML et al. Probing to bone infected pedal ulcers: a clinical sign of underlying osteomyelitis in diabetic patients. JAMA 1995; 273 (9): 721-723 Being unable to probe to bone with metallic instrument had a negative predictive value of 96-98% for diagnosing osteomyelitis Lavery et al. Probe-to-Bone Test for Diagnosis Diabetic Foot Osteomyelitis. Diabetes Care 2007; 30:270-274.  Bone Biopsy “Gold standard” for diagnosing Charcot vs. Osteomyelitis is bone biopsy with culture Biopsy will show bone and cartilage debris embedded in synovium Helpful to culture organisms in the bone because bone pathology is not very specific Before biopsy, patient needs to be off antibiotics for at least three half-lives Sequelae Foot and ankle deformity Increased pressure Ulceration Soft tissue and bone infection Partial amputation Limb loss 25%-30% chance of developing Charcot in the contralateral extremity Death Treatment Stage I – Ideally keep NWB in total contact cast or boot until consolidation occurs and/or temperature stabilizes – Recent studies have shown WB in boot or total contact cast can also stabilize foot if damage is in midfoot and not hindfoot – May take months (9 weeks – 11 months) Stage II – Continued protected weight bearing Stage III – Custom orthotics or braces Conservative Care Extra-depthor custom molded shoe and a pressure relieving orthotic – If not severe rocker- bottom deformity Total contact cast Cam boot CROW walker AFO (Arizona brace) Conservative Care External bone growth stimulators? Bisphosphonates? Calcitonin? Denosumab (Prolia)? – RANK-L antibody Surgical Treatment Should ideally wait until Eichenholtz stage 2 or 3 Can do surgery on stage 1 but will need to use ex-fix with caution  Surgical Treatment Exostectomies Arthrodesis procedures Realignment osteotomies – Can be achieved via external fixation, internal fixation or a combination of both Management of soft tissue and osseous infections Amputation – Partial foot – Below Knee or Above Knee Surgical Treatment Extensive medical workup is required to clear patient for surgery and more important for the postoperative healing period – NWB or PWB is typically required and can have a large impact on cardiopulmonary function Must optimize vascular status Renal disease has a large impact on outcomes Cardiac status – Ejection fraction of 55% required for minimal risk of postoperative cardiac complications Case Example Foot Fracture Dislocation due to Diabetes Mellitus and Charcot Radiographs  3D Printing Patient Education Surgical planning Student, resident, fellow education Research Reference Trepman et al, “Current Topics Review: Charcot Neuroarthropathy of the Foot and Ankle,” Foot and Ankle International, Jan 2005, page 46-63 Strotman et al, “Charcot Arthropathy of the Foot and Ankle.” Foot and Ankle International, Nov 2016. pg 1255-1263 Rosskopf AB, Loupatatzis C, Pfirrmann CWA, Böni T, Berli MC. The Charcot foot: a pictorial review. Insights Imaging. 2019 Aug 5;10(1):77. doi: 10.1186/s13244-019-0768-9. PMID: 31385060; PMCID: PMC6682845. Dardari D. An overview of Charcot's neuroarthropathy. J Clin Transl Endocrinol. 2020 Oct 28;22:100239. doi: 10.1016/j.jcte.2020.100239. PMID: 33251117; PMCID: PMC7677697.