Rhabdomyomatous mesenchymal hamartoma (RMH) is a rare, benign, congenital tumor of the dermis and subcutaneous tissue comprised of skeletal muscle and adipose and adnexal elements. Although the majority of cases are an incidental finding in otherwise healthy patients, some have been reported in association with other anomalies. We present a full-term boy evaluated on day 2 of life for two lesions located on the midline of the lower back and right buttock that each appeared clinically as an atrophic, pink plaque. Ultrasound of the midline lesion revealed an underlying lipomyelomeningocele with a tethered cord in the spinal canal. Histopathology of the right buttock cutaneous lesion was consistent with a diagnosis of RMH. Surgical excision was performed on the midline intradural lipoma and the lesion on the buttock was monitored clinically. Repeat biopsy of this site at 1 year of age revealed complete spontaneous regression. This case highlights three interesting features: the association with an occult spinal dysraphism lipomyelomeningocele and tethered cord, the clinical presentation of an atrophic plaque as opposed to the more commonly reported raised lesions, and the phenomenon of spontaneous regression of the lesion. Most importantly, this final feature of regression in our patient suggests that, in the absence of symptoms, clinical observation of RMH lesions is warranted for spontaneous regression for 1 to 2 years provided that no functional deficit is noted and that the cutaneous or deeper lesions are not causing a medical problem.

Objective: The objective is to evaluate the efficacy of using tibial bone marrow delivered to the chondral-bone interface (CBI) via percutaneous chondral bone interface optimization (PeCaBoo) as a therapy for knee osteoarthritis (OA). Study Design: A series of prospective cases were presented. Participants: Our study included 10 patients with medial or lateral compartment knee OA. Methods: With 1 cc of heparin pre-loaded in the syringe, 5 cc of tibial bone marrow was withdrawn from the proximal tibia. The resultant 6 cc of aspirate in the syringe was injected via PeCaBoo, 2 cc at a time, into the superior CBI and inferior CBI. The remaining 2 cc was injected via needle into the intra-articular joint space. Main Outcome Measurements: Patients had MRIs taken pre-procedure and 3 months post-procedure to measure bone edema and intra-articular matrix thickness. Patient-reported outcomes recorded included the Western Ontario and McMaster University Osteoarthritis Index (WOMAC) and the Numeric Paint Rating Scale (NRS), which were both obtained pre-procedure and post-procedure at 3, 6, and 12 months. Use of non-steroidal anti-inflammatories (NSAIDs) was recorded pre-and post-procedure as well. Results: Our study included 4 males and 6 females, with an average age of 63.5 years. The average follow-up time was 14 months, with a range of 13 -15 months. The mean WOMAC score was 58.2 points pre-procedure and 35.3 points post-procedure (p < 0.01). The mean NRS-Pain score was 8.6 points pre-procedure and 2.8 points post-procedure (p < 0.01). The matrix thickness increased by 14% on average at 3 months postprocedure (p < 0.01). The proportion of patients taking NSAIDs decreased by 60% after the PeCaBoo procedure. The subgroup of patients with tibial edema and knee OA had optimal outcomes. Conclusions: Tibial bone marrow stem cell delivered via PeCaBoo is a novel minimally-invasive treatment for knee OA, with potential to repair cartilage and improve knee pain and function. * Corresponding author. V. Vad et al.2

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