2015 ISAKOS Biennial Congress ePoster #1711

Novel Classification of Medial Compartment Osteoarthritis Based on Mechanical Alignment

Miten R. Sheth, MBBS, MS, DNB (Orth), Mumbai, Maharashtra INDIA
Jae Hwa Kim, MD, PhD, Seongnam-Si, Gyeonggi-do KOREA, REPUBLIC OF
Keun-Jung Ryu, MD, Seongnam-Si, Kyeonggi-do KOREA, REPUBLIC OF

Department of Orthopedic Surgery, Bundang CHA Hospital, CHA University, Seongnam-Si , Gyeonggi-do, USA

FDA Status Not Applicable

Summary: Medial compartment knee osteoarthritis can be classified, with the use of continuous variables, keeping in mind the overall alignment of the limb and to ensure uniformity in reporting clinical outcomes and research, surgeons should consider the routine use of Sheth's classification.

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Abstract:

Background

Proximal tibial osteotomy (PTO) has been shown to be effective for varus correction of medial compartment degenerative disease and is also used in cartilage and ligament surgery with concurrent malalignment. Multiple PTO implants have been developed – conventional plate and screw (CPS) was popular initially whereas PEEK intraosseous implants (PII) have gained recent popularity.

Hypothesis

CPS and PII will be equivalent at correcting varus deformity.

STUDY DESIGN
Retrospective cohort study.

Methods

44 PTO cases—22 CPS, 22 PII—were reviewed from a preoperative baseline to a mean of 12 months radiographically (range: 4-37) and 20 months clinically (range: 13-33). Seven imaging measurements (limb mechanical axis, weight bearing line location along the tibial plateau (WBL), femoral axis-femoral condyle angle (FAFC), tibial plateau-tibial shaft angle (TPTS), tibial slope, Insall-Salvati ratio (ISR), Caton Deschamps index (CDI)) where recorded alongside complications, including those involving implant removal.

Results

At 0-6 months, both cohorts showed significant WBL, TPTS, and axial deformity improvements. CPS corrected from a mean axial deformity of 5.5° to -0.5° (p<0.0001) whereas PII corrected from 6.6° to -1.6° (p<0.0001).

CPS did not alter ISR and CDI at 0-6 months but affected both measures at 6-12 and 12-26 months (p<0.01). PII affected ISR throughout followup (p<0.05 at 0-12 months) without significantly perturbing CDI. Neither implant affected FAFC or tibial slope. At 12-26 months, remaining patients had deformities of 1.45° (CPS) and -1.60° (PII). At 24 months, 8 CPS implants had been removed (4 pain +/- instability, 4 subsequent reconstructive surgery) whereas all PII implants were in place, suggesting better PII implant tolerance by patients. Of note, PII implants are drillable, allowing for subsequent reconstruction without removal.

Conclusion

PII was found to be effective at maintaining axial correction with concurrent decreased patellar height perturbation and increased implant retention compared to CPS.