Samilson and Prieto Classification for Glenohumeral OA

The Samilson and Prieto classification is a widely used system for grading glenohumeral joint osteoarthritis based on the size of inferior humeral osteophytes. This classification was originally developed for assessing glenohumeral osteoarthritis in the setting of glenohumeral instability, but it has gained popularity due to its simplicity and reproducibility.3 The system consists of three grades:

Grade I (Mild):

• Inferior humeral and/or glenoid exostosis measuring less than 3 mm in height1

Grade II (Moderate):

• Inferior humeral and/or glenoid exostosis measuring 3 mm to 7 mm
• Slight glenohumeral joint irregularity may be present1

Grade III (Severe):

• Inferior humeral and/or glenoid exostosis measuring greater than 7 mm
• Glenohumeral joint narrowing and sclerosis are evident1

This classification system is based on true anteroposterior (AP) shoulder radiographs.2 It focuses primarily on the presence and size of osteophytes, which are considered a hallmark of osteoarthritis.

Studies have shown that the Samilson-Prieto classification has high intraobserver and interobserver reliability. In one study, the intraobserver reliability was 0.907 and 0.965 for two different observers, while the interobserver reliability was 0.851.3 These values indicate excellent agreement and consistency when using this classification system.

It's important to note that while the Samilson-Prieto classification is useful for its simplicity, it may not capture all aspects of glenohumeral osteoarthritis, such as glenoid morphology or humeral head subluxation. For a more comprehensive assessment, especially in surgical planning, additional classification systems like the Walch classification may be used in conjunction with Samilson-Prieto.3

Kellgren-Lawrence Classification for Glenohumeral OA

The Kellgren-Lawrence (KL) classification system is widely used to grade the severity of osteoarthritis (OA) in various joints, including the glenohumeral joint.4 While originally developed for knee OA, it has been adapted for use in shoulder radiographs. The KL classification for glenohumeral joint osteoarthritis consists of five grades:

Grade 0: No radiographic features of osteoarthritis

Grade 1 (Doubtful):

• Doubtful joint space narrowing
• Possible osteophytic lipping

Grade 2 (Mild):

• Definite osteophytes
• Possible joint space narrowing

Grade 3 (Moderate):

• Moderate multiple osteophytes
• Definite narrowing of joint space
• Some sclerosis
• Possible deformity of bone ends

Grade 4 (Severe):

• Large osteophytes
• Marked narrowing of joint space
• Severe sclerosis
• Definite deformity of bone ends

This classification system is typically applied to anterior-posterior (AP) radiographs of the glenohumeral joint. It's important to note that osteoarthritis is generally considered present at grade 2 or higher, although it is of minimal severity at this stage.4

The KL classification for glenohumeral OA helps standardize the assessment of radiographic changes and aids in clinical decision-making. However, it's worth noting that while this system is widely used, there may be some variability in its application and interpretation among different observers.5

For a more specific assessment of glenohumeral joint osteoarthritis, some clinicians may prefer using the Samilson-Prieto classification, which focuses on the size of inferior humeral and/or glenoid exostoses.1

Walch Classification for Glenoid Morphology in Glenohumeral OA

The Walch classification is a widely used system for categorizing glenoid morphology in glenohumeral osteoarthritis. Originally described by Walch et al. in 19996 and later modified,7 it includes the following types:

Type A: Centered humeral head

• A1: Minor central erosion
• A2: Major central erosion, humeral head protruding into the glenoid cavity

Type B: Posterior humeral head subluxation

• B1: Narrowing of posterior joint space, subchondral sclerosis, osteophytes
• B2: Biconcave glenoid with posterior rim erosion and retroversion
• B3: Monoconcave with posterior wear, >15° retroversion or >70% posterior humeral head subluxation, or both

Type C: Dysplastic glenoid

• C1: >25° retroversion regardless of erosion
• C2: Biconcave, posterior bone loss, posterior humeral head translation

Type D: Glenoid anteversion or anterior humeral head subluxation <40°

This classification system is typically assessed using CT scans, with 3D reconstructions improving reliability.8 It aids in preoperative planning and decision-making for shoulder arthroplasty, helping surgeons address specific glenoid wear patterns and humeral head positioning.

The Walch classification has evolved to better capture severe pathologies, with the addition of B3, C2, and D subtypes in the modified version.7 This system's reliability has improved with these modifications, though some variability in interpretation may still exist among observers.9

References

1. Samilson RL, Prieto V. Dislocation arthropathy of the shoulder. J Bone Joint Surg Am. 1983;65(4):456-460.
2. Linke PM, Zemke K, Ecker NU, Neumann J, Werner AW. Standard radiological classification of glenohumeral osteoarthritis does not correlate with the complexity of the arthritic glenoid deformity. Arch Orthop Trauma Surg. 2022;142(7):1413-1420. doi:10.1007/s00402-021-03758-7
3. Elsharkawi M, Cakir B, Reichel H, Kappe T. Reliability of radiologic glenohumeral osteoarthritis classifications. J Shoulder Elbow Surg. 2013;22(8):1063-1067. doi:10.1016/j.jse.2012.11.007
4. Kohn MD, Sassoon AA, Fernando ND. Classifications in Brief: Kellgren-Lawrence Classification of Osteoarthritis. Clin Orthop Relat Res. 2016 Aug;474(8):1886-93. doi: 10.1007/s11999-016-4732-4. Epub 2016 Feb 12. PMID: 26872913; PMCID: PMC4925407.
5. Hayes B, Kittelson A, Loyd B, Wellsandt E, Flug J, Stevens-Lapsley J. Assessing Radiographic Knee Osteoarthritis: An Online Training Tutorial for the Kellgren-Lawrence Grading Scale. MedEdPORTAL. 2016 Nov 18;12:10503. doi: 10.15766/mep_2374-8265.10503. PMID: 30984845; PMCID: PMC6440422.
6. Walch G, Badet R, Boulahia A, Khoury A. Morphologic study of the glenoid in primary glenohumeral osteoarthritis. J Arthroplasty. 1999;14(6):756-760. doi:10.1016/s0883-5403(99)90232-2
7. Bercik MJ, Kruse K 2nd, Yalizis M, Gauci MO, Chaoui J, Walch G. A modification to the Walch classification of the glenoid in primary glenohumeral osteoarthritis using three-dimensional imaging. J Shoulder Elbow Surg. 2016;25(10):1601-1606. doi:10.1016/j.jse.2016.03.010
8. Vo KV, Hackett DJ, Gee AO, Hsu JE. Classifications in Brief: Walch Classification of Primary Glenohumeral Osteoarthritis. Clin Orthop Relat Res. 2017 Sep;475(9):2335-2340. doi: 10.1007/s11999-017-5317-6. Epub 2017 Mar 17. PMID: 28315182; PMCID: PMC5539019.
9. Kidder JF, Rouleau DM, Defranco MJ, Pons-Villanueva J, Dynamidis S. Revisited: Walch Classification of the Glenoid in Glenohumeral Osteoarthritis. Shoulder & Elbow. 2012;4(1):11-15. doi:10.1111/j.1758-5740.2011.00151.x