Working Diagnosis:
Non-acute incomplete fracture of the fibular sesamoid

Treatment:
2 ml of leukocyte-poor platelet-rich plasma (PRP) was injected into the first MTP joint under ultrasound guidance using a dorsal approach Case Photo #4 . After 1 day of non-weight bearing followed by 2 days of partial weight-bearing, weight-bearing as tolerated and physical therapy was initiated along with progression back to running.

Outcome:
11 weeks following the initial visit, the patient reported his pain had improved by 80%. He had sporadic diffuse pain under the right great toe with standing but not with running or activity. He was discharged from PT, returned to full training and running, and was preparing to go on a hiking trip.

One year after the PRP injection, the patient reported he had no pain, had gone on several strenuous hiking trips, has been running fully with no issues, and, in fact, is more active since the injection due to lack of pain and discomfort.

Author's Comments:
Within the FHB tendon are the hallux sesamoid bones that assist in absorbing and dispersing forces at the metatarsal head. Sesamoid pain can be due to irritation of the sesamoids, including sesamoid fractures. These fractures are usually caused by repetitive high-impact activities, including long-distance running. There is a dearth of literature on PRP for sesamoiditis and fracture; only one case study has been published. PRP works by delivering concentrated growth factors and pro-inflammatory cytokines to the fracture site and inducing angiogenesis in the treatment area to improve blood flow.

Editor's Comments:
More than half of body weight is transmitted through the first MTP joint during gait, and the sesamoids are susceptible to inflammation, avascular necrosis, fracture, or sprain of bipartite sesamoid. Injury is usually seen in young athletes, particularly runners or dancers who repetitively push off the ball of their feet during jumping or running.

In this case it appeared as though there was sesamoid pathology as well as synovitis and chondral degeneration of the 1st MTP joint - both contributing to plantar foot pain. A healing fracture of the sesamoid could partially explain some of his lingering discomfort, however the other issues could play a role as well. It may be that the injection used successfully treated his synovitis and chondral wear, especially as it was injected into the 1st MTP.

That being said, the plan to try a diagnostic/ therapeutic injection using a leukocyte-poor PRP substrate and injecting into the 1st MTP joint was wise for several reasons. First, the MTP joint is likely an easier and more accessible anatomic location for injection of substrate. Second, leukocyte-poor PRP preparations have shown early promise particularly for intra-articular use since they are thought to be less inflammatory to the joint environment. Lastly, the athlete improved quite rapidly after the PRP injection, so 1st MTP joint synovitis and chondral wear appears to have been adequately addressed and has allowed the athlete to return to activity.

It would be interesting to see what a repeat MRI would reveal one year after the injection.

References:
Wempe MK, Sellon JL, Sayeed YA, Smith J. Feasibility of first metatarsophalangeal joint injections for sesamoid disorders: a cadaveric investigation. PM R. 2012;4(8):556-560.

Glasoe WM, Yack HJ, Saltzman CL. Anatomy and Biomechanics of the First Ray. Phys Ther. 1999;79(9):854-859.

DeLisa JA, Bockeneck W, Gans BM, Chase J, Robinson LR. Physical Medicine and Rehabilitation - Principles and Practice. (Frontera WR, DeLisa JA, Chae J, Basford JR, Bockenek WL, Robinson, eds.). Wolters Kluwer; 2020.

Le HM, Stracciolini A, Stein CJ, Quinn BJ, Jackson SS. Platelet rich plasma for hallux sesamoid injuries: a case series. Phys Sportsmed. Published online August 18, 2021:1-4.

Zhang Y, Xing F, Luo R, Duan X. Platelet-rich plasma for bone fracture treatment: A systematic review of current evidence in preclinical and clinical studies. Front Med. 2021;8:676033.

Zhang N, Wu YP, Qian SJ, Teng C, Chen S, Li H. Research progress in the mechanism of effect of PRP in bone deficiency healing. Scientific World Journal. 2013;2013:134582.

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