Albert Ferrando1, Luis Natera2,3, Berta Buch4,5, Paolo Consigliere6, Juan Bruguera6,7, Giuseppe Sforza6, Ehud Atoun8, Ofer Levy6. 1. Traumatology and Orthopaedic Surgery Department, Hospital Universitari Sant Joan de Reus, Avinguda del Doctor Josep Laporte 2, 43204, Tarragona, Reus, Spain. 2. Hospital General de Granollers, Avinguda Francesc Ribas S/N, 08402, Granollers, Spain. luisgerardonaterac@gmail.com. 3. Hospital Asepeyo Sant Cugat, Av. Alcalde Barnils, 54, 60, 08174, Barcelona, Spain. luisgerardonaterac@gmail.com. 4. Hospital General de Granollers, Avinguda Francesc Ribas S/N, 08402, Granollers, Spain. 5. Universitat Autònoma de Barcelona, Campus Bellaterra, Cerdanyola del Vallès, Barcelona, Spain. 6. Reading Shoulder Unit, Royal Berkshire Hospital and Berkshire Independent Hospital Reading, Berkshire, RG1 6UZ, UK. 7. Hospital San Juan de Dios Pamplona, Sreet Beloso Alto 3, 31006, Pamplona (Navarra), Spain. 8. Faculty of Health Sciences, Barzilai Medical Center Campus, Ben-Gurion University, Ashkelon, Israel.
Abstract
BACKGROUND: Revision shoulder arthroplasty may involve the need to remove a well-fixed humeral stem. To avoid this, convertible platform systems have been introduced. The biomechanics of reverse total shoulder arthroplasty (rTSA) differs from anatomic shoulder arthroplasty (aTSA). The different humeral osteotomy and soft tissue tension may jeopardize the optimal results of the converted rTSA. The aim was to evaluate the radiographic parameters of soft tissue distraction when converting an aTSA to rTSA in a platform system and assess the capability of conversion without "over-stuffing" the shoulder in the "best-case scenario". METHODS: Radiographic analysis of soft tissue distraction parameters: difference in acromio-humeral distance, difference in lateral humeral offset and difference in latero-inferior displacement were evaluated in aTSA and in the converted rTSA in six different implants. Image analysing software was used on 10 non-deformed osteoarthritic shoulder X-rays to simulate conversion. RESULTS: The greatest increase in arm length was found for Tornier Ascend Flex (26.8 ± 3.6 mm) while the smallest increase was observed with Lima SMR (19.3 ± 4 mm). The humerus remained most lateralized with the Zimmer Anatomical/Inverse ( - 1.4 ± 2.9 mm) while Lima SMR ( - 15.8 ± 2.7 mm) was more medialized. The greatest increase in latero-inferior distance was found in the onlay systems. A group analysis of onlay rTSA showed an increase of 46% in arm length (p < 0.0001), 83% larger humeral offset (p < 0.0001) and 144% increase in latero-inferior distraction (p < 0.0001) when compared to inlay rTSA. CONCLUSION: The conversion of aTSA to rTSA using a convertible platform system may lead to significant increase in radiographic parameters corresponding to soft tissue tension. This may alter the biomechanics, restrict the convertibility or jeopardize the optimal clinical outcome of rTSA even in the best-case scenario.
BACKGROUND: Revision shoulder arthroplasty may involve the need to remove a well-fixed humeral stem. To avoid this, convertible platform systems have been introduced. The biomechanics of reverse total shoulder arthroplasty (rTSA) differs from anatomic shoulder arthroplasty (aTSA). The different humeral osteotomy and soft tissue tension may jeopardize the optimal results of the converted rTSA. The aim was to evaluate the radiographic parameters of soft tissue distraction when converting an aTSA to rTSA in a platform system and assess the capability of conversion without "over-stuffing" the shoulder in the "best-case scenario". METHODS: Radiographic analysis of soft tissue distraction parameters: difference in acromio-humeral distance, difference in lateral humeral offset and difference in latero-inferior displacement were evaluated in aTSA and in the converted rTSA in six different implants. Image analysing software was used on 10 non-deformed osteoarthritic shoulder X-rays to simulate conversion. RESULTS: The greatest increase in arm length was found for Tornier Ascend Flex (26.8 ± 3.6 mm) while the smallest increase was observed with Lima SMR (19.3 ± 4 mm). The humerus remained most lateralized with the Zimmer Anatomical/Inverse ( - 1.4 ± 2.9 mm) while Lima SMR ( - 15.8 ± 2.7 mm) was more medialized. The greatest increase in latero-inferior distance was found in the onlay systems. A group analysis of onlay rTSA showed an increase of 46% in arm length (p < 0.0001), 83% larger humeral offset (p < 0.0001) and 144% increase in latero-inferior distraction (p < 0.0001) when compared to inlay rTSA. CONCLUSION: The conversion of aTSA to rTSA using a convertible platform system may lead to significant increase in radiographic parameters corresponding to soft tissue tension. This may alter the biomechanics, restrict the convertibility or jeopardize the optimal clinical outcome of rTSA even in the best-case scenario.
Entities:
Keywords:
Anatomic total shoulder arthroplasty; Conversion platform system; Humeral offset; Inlay and onlay design; Reverse total shoulder arthroplasty; Revision shoulder arthroplasty
Authors: Judd S Day; Edmund Lau; Kevin L Ong; Gerald R Williams; Matthew L Ramsey; Steven M Kurtz Journal: J Shoulder Elbow Surg Date: 2010-06-15 Impact factor: 3.019
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