MISHA - Medial Implantable Shock Absorber for Knee OA

What It Is

Indications (FDA-Approved)

Surgical Technique (Key Steps)

1. Incision: Longitudinal medial knee incision, 1 cm proximal to the medial epicondyle down to the pes anserinus insertion (~3 cm medial to tibial tubercle), exposing the superficial MCL and medial joint line.
2. Femoral anisometric point: The most critical step - establishes a 4 mm posterior condylar offset in 90° flexion vs. full extension, ensuring the implant loads in extension and relaxes in flexion (preventing over-constraint).
3. Trial implant: Placed to confirm anisometry, appropriate loading, and relaxation dynamics.
4. Final fixation: Titanium femoral and tibial baseplates each fixed with 3 unicortical titanium locking screws.
5. Closure: Standard layered closure; no immobilization required.

Key Advantages Over Alternatives

Outcomes (Evidence)

• In a prospective FDA-supervised study vs. HTO: MISHA showed superior results in pain, function, adverse events, and conversion surgery at 24 months (PMID: 40539037).
• Short-term: 100% arthroplasty-free survival at 2 years, 85% at 5 years.
• Patients reported 1/4 of pre-operative knee pain at 2 years.
• Most patients go home the same day; average time to full weight bearing without crutches ~13.4 days.
• Return to sport is faster than ACL reconstruction in many patients (PMID: 40529534).

Limitations

• Long-term data (>5 years) is still lacking given the novelty of the device.
• Technically demanding - anisometric point placement is unforgiving; malposition leads to poor outcomes.
• May cause medial soft tissue irritation.
• Insurance coverage is variable - many payers still consider it investigational.
• Not a cure for OA; disease progression can still occur.

MISHA Knee System - Recent Clinical Outcomes & Patient Satisfaction

Key Evidence Summary (by study)

1. Pivotal IDE Study - 5-Year Data (JBJS, June 2026) - Most Recent

Source: Moximed press release on Ortho Spine News, citing JBJS publication June 2026.

2. Gomoll et al. - KSSTA (2023) - Foundational 5-Year Study

• 85% survival-from-arthroplasty at 5 years in working-age patients with medial compartment OA
• First large published mid-term survivorship dataset
• Knee Surgery, Sports Traumatology, Arthroscopy, 2023;31(8):3307-3315

3. Diduch et al. - ISA vs. HTO Comparison - Cartilage (2023)

• ISA group showed superior pain relief AND function vs. HTO at 2 years
• Cited in PMID: 40539037

4. Systematic Review - Anzillotti et al. - Cartilage (2026)

• 4 ISA studies reviewed; all showed consistent WOMAC pain and function improvement
• Mean WOMAC pain improvement: 71%, function improvement: 69%
• ISA showed higher 2-year arthroplasty-free survival than HTO or non-operative comparators
• 3-year survivorship in one subgroup: 97.3%
• Conclusion: "ISA can provide meaningful short-to-mid-term symptom relief and delay arthroplasty in carefully selected patients" - but larger independent RCTs needed
• Evidence certainty rated low-to-moderate due to small heterogeneous cohorts

5. Van der List & Flanigan - Video J Sports Med (2026)

• 90% survivorship at 3 years, 85% at 5 years
• Weightbearing at 13 days vs. 59 days for HTO
• "Implant is generally safe and leads to clinical improvement in nearly all cases"
• Level 3 evidence

6. Biomechanical Data

• 32% reduction in peak medial compartment force during walking (Morgan et al., J Orthop Research, 2019)
• Pain cut in half as early as 3 months post-op

Patient Satisfaction Data

• ¼ of pre-operative pain reported at 2 years
• 91% of US patients discharged same day as surgery
• Return to full weight-bearing (no crutches) at average 13.4 days
• Patients report return to sport faster than ACL reconstruction in many cases
• Patient testimonials describe return to mountain climbing at 8-10 weeks (5 years post-op)

Critical Appraisal - What the Evidence Does NOT Yet Show

Bottom Line