Isolated Antero medial Osteoarthritis on the rise among Indian Patients Undergoing TKA

Isolated antero-medial osteoarthritis (AMOA) of the knee is a distinct pattern of arthritis. Medial arthritis of the knee in select patients can be managed with uni-compartmental arthroplasty (UKA), with studies showing shorter hospital stay, faster rehabilitation and reduced medical complications in the post-operative period compared to TKA. However, the prevalence of AMOA in Indian patients with osteoarthritis of the knee is unknown.

Adarsh Annapareddy et al conducted a study to evaluate the prevalence of AMOA in patients undergoing primary TKA for OA. A prospective evaluation was done in 2518 knees in 1936 patients who were selected for primary TKA. Pre-operative radiographs were screened based on the Oxford UKA Radiological decision aid and diagnosis of AMOA was established. All 2518 knees underwent primary total knee arthroplasty.

AMOA Pattern of arthritis was confirmed intraoperatively, with the following criteria, which were documented photographically.

1. Intact ACL

2. Functional ACL with linear striations or fibrillations

3. Normal lateral compartment cartilage

4. Antero-medial OA on the resected tibial biscuit

5. Absence of lateral patellar facet arthritis/ cartilage loss over the trochlea.

Cases with AMOA arthritic wear pattern were considered amenable for UKA if radiographs showed intact lateral joint space, intra-operatively those with intact and functional ACL, acceptable patellofemoral wear (Outerbridge I–II)

.Key findings of the study were:

• 2518 knees (1936 patients with 1354 unilateral TKA and 582 bilateral TKA).

• There was a female preponderance with 1715 (68.1%) knees in females and 803 (31.89%) knees in male patients.

• The average age was 62 years (range 48–72 years).

• The average BMI of all the patients was 30.5 (28 to 35).

• Prevalence of AMOA in 46.94% knees, who were amenable for UKA.

• Obese patients were more likely to have a damaged or non-functional ACL and more likely to have a high degree of wear, not amenable for UKA (p<0.05).

• Non-functional ACL was associated with higher prevalence of posterior extension of arthritic wear.

The authors concluded that – "This study demonstrated a high prevalence (46.94%) of anteromedial osteoarthritis (AMOA) in Indian patients undergoing primary total knee arthroplasty. These patients were all amenable to medial unicompartmental arthroplasty based on Oxford selection criteria. Patient selection is important for improving outcomes after TKA or UKA. Future studies are warranted to compare outcomes of both UKA and TKA in patients with isolated AMOA of the knee."

Further reading:

High Prevalence of Isolated Antero medial Osteoarthritis (AMOA) in Indian Patients Undergoing Primary Total Knee Arthroplasty

Adarsh Annapareddy, Deepesh Daultani, A. V. Gurava Reddy et al

Indian Journal of Orthopaedics (2022) 56:1774–1781

https://doi.org/10.1007/s43465-022-00710-8