Stem Cells Fix Torn Meniscus? But Wait!

The recent publication of two high-quality randomized controlled trials makes the evidence base to guide management of symptomatic meniscal tear more exciting, but also more confusing.

Both investigators and clinicians have been concerned that partial meniscectomy is associated with greater progression of osteoarthritis than nonoperative treatment.  To address this problem by encouraging meniscal regeneration, Vangsness and colleagues have performed a randomized controlled trial, injecting one of three substances into the knee joint 7-10 days after arthroscopic partial meniscectomy in 59 patents with meniscal tear: (1) a lower concentration of mesenchymal stem cells with hyaluronic acid vehicle, (2) a higher concentration of the mesenchymal stem cells with vehicle, or (3) vehicle alone.¹

After one and two years, the stem cell recipients appeared to have greater improvement in pain than the control patients.  An increase in meniscal volume as measured by MRI was also more likely among those receiving stem cells. 

However, there are several reasons why these results will need to be replicated:  The sample size was small, the proportion who actually experienced increased volume at two years was also small (15%), and that proportion was concentrated among those who received the lower dose of stem cells. Finally, the study was industry-sponsored.

Nevertheless, the study provides an exciting initial proof of concept for meniscal regeneration following arthroscopic partial meniscectomy. But beware: The basic assumption that arthroscopic partial meniscectomy is an effective procedure has been challenged.

That challenge has come from a carefully performed, sham-controlled trial in patients with degenerative meniscal tear. In this study by Sihvonen and colleagues,² the sham and partial meniscectomy groups had virtually identical pain relief and functional improvement after one year. 

This observation raises a fundamental question: Do the risks of accelerated osteoarthritis observed with partial meniscal resection justify undertaking the procedure in the first place? 

For now, there’s good reason to offer nonoperative therapy before considering arthroscopic partial meniscectomy, and if a surgeon does intervene, to sacrifice as little meniscal tissue as possible.

References:

1.  Vangsness CT, Farr J, Boyd J, et al. Adult Human Mesenchymal Stem Cells Delivered via Intra-Articular Injection to the Knee Following Partial Medial Meniscectomy: A Randomized, Double-Blind, Controlled Study. J Bone Joint Surgery  (2014) 96:90-98.

2.  Sihvonen R, Paavola M, Malmivaara A, et al for the Finnish Degenerative Meniscal Lesion Study (FIDELITY) Group. Arthroscopic Partial Meniscectomy versus Sham Surgery for a Degenerative Meniscal TearN Engl J Med  (2013) 369:2515-2524.