Factors of patellar instability: An anatomic radiographic study
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We analyzed the radiographs and computed tomography (CT) scans of 143 knees operated on for symptomatic patellar instability and 67 contralateral asymptomatic knees, togcther with 190 control knee radiographs and 27 control knee scans, to determine the factors affecting patellar instability. Four factors were relevant in knees with symptomatic patellar instability: (1)Trochlear dysplasia (85%), as defined by the crossing sign (96%) and quantitatively experessed by the trochlear bump, pathological above 3 mm or more (66%), and the trochlear depth, pathologic at 4 mm or less. (2)Quadriceps dysplasia (83%), defined as present when the patellar tilt in extension is more than 20% on the CT scans. (3)Patella alta (Caton-Deschamps) index greater than or equal to 1.2 (24%). (4)Tibial tuberosity-trochlear groove, pathological when greater than or equal to 20 mm (56%). The factors appeared in only 3%–6.5% of the control knees. The etiology of patellar instability is multifactorial. Determination of the factors permits an effective elective therapeutic plan which aims at correcting the anomalies present.
Key wordsPatellar height Patellar tilt patellar instability Trochlear dysplasia Surgical treatment
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- 1.Albee FH (1915) The bone graft wedge in the treatment of habitual dislocation of the patella. Med Rec 88:257–259Google Scholar
- 2.Blackburne JS, Peel TE (1977) A new method of measuring patellar height. J Bone Joint Surg 59:241–242Google Scholar
- 3.Brattström H (1964) Shape of the intercondylar groove normally and in recurrent dislocation of the patella. Acta Orthop Scand Suppl 68:1–148Google Scholar
- 7.Houghston JC (1968) Subluxation of the patella. J Bone Joint Surg [Am] 50:1003–1026Google Scholar
- 8.Hughston JC, Walsh WM, Puddn G (1984) Patellar subluxation and dislocation. Saunders, PhiladelphiaGoogle Scholar
- 12.Laurin CA, L'Evesque HP, Dussault R, Labelle H, Peides JP (1978) The abnormal lateral patellofemoral angle. A diagnostic, roentgenographic sign of recurrent patellar sublucation. J Bone Joint Surg [Am] 60:55–60Google Scholar
- 13.Maldague B, Malghem J (1985) Apport du cliché de profil du genou dans le dépistage des instabilités rotuliennes. Rapport préliminaire. Rev Chir Orthop 71 [Suppl II]:5–13Google Scholar
- 14.Merchant AC, Mercer RL, Jacobsen RH, Cool CR (1974) Roentgenographic analysis of patellofemoral congruence. J Bone Joint Surg [Am] 56: 1391–1396Google Scholar