We present a hip mapping system to describe chondral lesions within the hip, and an assessment of its inter-observer reliability and ease of use. The mapping system divides the acetabular articular surface into ten zones (five inner and five outer) and the femoral head into five zones using easily identifiable features.

This study was performed by six surgeons during hip arthroscopy of 60 patients. During each operation, one of the surgeons identified up to three small intra-articular features to several (one, two or three) of the other five surgeons. Each surgeon examined the hip independently without discussion and recorded the locations on a hip map. If two surgeons had observed a point, this provided one pair to assess agreement; three or four surgeons provided three or six pairs respectively. Each observation of a point by a pair of surgeons (a point-pair) provided one opportunity for assessment of agreement.

One Hundred and Fifty Four points were mapped by two, three or four surgeons, giving 353 point-pairs for assessment. In 325 cases (92%), the pair of surgeons were in agreement, designating the point as within the same zone. On 23 (8%) occasions, there was disagreement but always across a boundary between adjacent zones. Disagreements were more common about points on the femoral head (15) than on the acetabulum (13). Disagreements in acetabulum occurred equally at each radial boundary but only rarely between inner and outer acetabular zones. All surgeons reported that they found the system easy to use. There was no difference in the level of disagreement between more and less experienced surgeons or a learning effect with time.

Inter-observer reliability of this mapping system was 92%, supporting the use of a zone based mapping system in clinical practice. This map shows a good balance between precision and reliability.