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Short and Mid-Term Outcomes of the Subchondroplasty Procedure for the Treatment of Bone Marrow in Patients with Knee Osteoarthritis

      Introduction

      Bone marrow edema (BME) is a negative prognostic factor for patients with knee osteoarthritis (KOA). BME is strongly associated with pain, decreased function, structural deterioration and rapid progression to total knee arthroplasty (TKA). Subchondroplasty (SCP) (Knee Creations, Zimmer, Warsaw, IN) directly addresses BME in the setting of KOA by injecting calcium phosphate cement into the area of BME.

      Methods

      A retrospective chart review with follow-up questionnaire was conducted on SCP patients in short-term and mid-term (>2 years). All patients failed conservative measures and were candidates for TKA. The questionnaire addressed symptoms before and after SCP, further interventions, the perception of and willingness to undergo SCP again.

      Results

      133 of 143 subchondroplasty patients responded. The average patient was 57 years old (38-84 years) and 47% male. The average follow-up for short-term patients was 14.6 (4-22) months and for mid-term patients was 32.1 (24-43) months. Pain score decreased from 8.3 pre-op to 3.4 post-op in both groups. 35% in the short-term group required injections, increasing to 41% in the mid-term. The short-term group demonstrated satisfaction of 8.3 out of 10, with 82% willing to undergo SCP again and 89% recommending SCP. In the mid-term group, satisfaction increased to 8.5 with 95% willing to undergo SCP again and 96% recommending the procedure. In all, 32 patients (25%) progressed to TKA (Figure 1) at an average of 17.8 months, with 22 (69%) of these occurring before 2 years.

      Conclusion

      SCP is an effective and well received treatment for patients with KOA and BME. In patients who failed conservative measures and were considering TKA, excellent results are seen at 2.5 years follow-up with only 25% of patients requiring TKA. Of all patients not requiring TKA, 93% would undergo SCP again and 98% would recommend it.