Table 2. The Paprosky's Classification System for Acetabular Deficiencies.

Type	Superior migration*	Ischial lysis†	Med migration‡	Teardrop lysis§
1	Insignificant	None	None	None
2A	Insignificant	Mild	Grade I	Mild
2B	Insignificant to significant	Mild	Grade II	Mild
2C	Insignificant	Mild	Grade III	Moderate to severe
3A	Significant	Moderate	Grade II or III	Moderate to severe
3B	Significant	Severe	Grade III	Moderate to severe

^* Insignificant: <3 cm above superior transverse obturator line, Significant: >3 cm above superior transverse obturator line.

^† Mild: 0 to 7 mm below superior transverse obturator line, Moderate: 7 to 14 mm below superior transverse obturator line, Severe: 15-mm lysis.

^‡ Grade I: lateral to Kohler's line, Grade II: migration to Kohler's line, Grade II+: medial expansion of Kohler's line into pelvis, Grade III: migration into pelvis with violation of Kohler's line, Grade III+: marked migration into pelvis.

^§ Mild: minimal loss of the lateral border, Moderate: complete loss of lateral border, Severe: loss of lateral and medial borders.