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Recurrent Horizontal Dislocation of the Patella in the Sagittal Plane. A Case Report*
NOBUYUKI YOSHINO, M.D.†; SHINRO TAKAI, M.D.†; SHINICHIRO NAKAMURA, M.D.†; TAKUHIRO MANABE, M.D.†; YASUSUKE HIRASAWA, M.D.†, KYOTO, JAPAN
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Investigation performed at the Department of Orthopaedic Surgery, Kyoto Prefectural University of Medicine, Kyoto
JBJS Case Connector, 1996 Feb 01;78(2):278-80
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Dislocation of the patella usually occurs to the lateral side, in the coronal plane. Horizontal dislocation of the patella in the sagittal plane is rare; we are aware of thirty-five previously reported cases, all of which involved dislocation into the intra-articular space between the femur and tibia3-6,10,12. The patient in the present report had a dislocation of the patella in which the patella rotated in the sagittal plane to lie horizontally at the level of the suprapatellar pouch without rupture of the patellar ligament. To our knowledge, there is no previous report of this condition having been treated operatively1,7,8,14.

*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.

†Department of Orthopaedic Surgery, Kyoto Prefectural University of Medicine, Kawaramachi Hirokoji, Kamigyo-ku, Kyoto 602, Japan.

*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.
†Department of Orthopaedic Surgery, Kyoto Prefectural University of Medicine, Kawaramachi Hirokoji, Kamigyo-ku, Kyoto 602, Japan.
 
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+FIG. 1 Lateral radiograph of the right knee, made in June 1993, demonstrating horizontal dislocation of the patella in the sagittal plane.
 
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+Figs. 2-A, 2-B, and 2-C: Radiographs of the knee, made in July 1993. Fig. 2-A: Anteroposterior radiograph showing hypertrophic changes.
 
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+Lateral radiograph showing osteophytes of the patella and femur. There is patella alta according to the Insall-Salvati ratio of 1.35.
 
 
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+Figs. 3-A, 3-B, and 3-C: Lateral radiographs made during fluoroscopy without anesthesia. Fig. 3-A: The knee in full extension.
 
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+Fig. 3-B: When the quadriceps muscle was contracted, the inferior edge of the patella lay superior to the osteophyte at the margin of the femoral articular surface.
 
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+Fig. 3-C: When slight pressure was applied to the patella, the osteophyte at the inferior margin of the patella could be locked posterior to the edge of the femoral osteophyte.
In December 1992, a sixty-five-year-old man tripped and fell while walking, after which he found the right knee to be locked in a slightly flexed position, with a prominence anteriorly at the level of the patella and a concavity distal to the prominence. He was able to manipulate the knee and reduce the dislocation without medical assistance. In May 1993, he had a similar injury of the knee but again was able to manipulate the patella back into normal position.
A third dislocation occurred when the patient was getting into an automobile in June 1993. He felt sharp pain, and this time he was unable to manipulate the patella back into normal position. He was seen at a local hospital—the first time that he consulted a physician for this condition—where a lateral radiograph revealed that the patella was lying almost horizontally, with its articular surface facing superiorly; an osteophyte on the inferior edge of the patella was held by an anterior osteophyte on the femur (Fig. 1). The patella was easily reduced by full passive extension of the knee. After reduction, the patient could walk and even run without pain. He could raise the limb against gravity with the knee extended and had no tender point about the knee.
In July 1993, the patient came to our hospital because of patellar pain. Radiographs of the knee demonstrated osteoarthrosis of the patellofemoral joint and formation of spurs (Figs. 2-A, 2-B, and 2-C). The Insall-Salvati ratio was 1.35, indicating patella alta, although the Blackburne-Peel ratio was 0.83, which is within the normal range. Fluoroscopy without anesthesia demonstrated that, during active contraction of the quadriceps muscle, the tip of the osteophyte on the inferior edge of the patella moved superior to the osteophyte on the superior margin of the articular surface of the medial femoral condyle. The inferior edge of the patella could be made to catch on the femoral osteophyte by application of slight pressure to the patella or by passive flexion of the knee (Figs. 3-A, 3-B, and 3-C); when this occurred, the patient had discomfort. The femoral and patellar osteophytes were resected in an open arthrotomy on July 22, 1993; the patellar ligament and the rest of the extensor mechanism appeared intact. The knee was not immobilized, and the postoperative course was uneventful. The patient reported no difficulty when he was last seen eleven months after the operation.
Horizontal dislocation of the patella in the sagittal plane is a rare injury; we found reports of thirty-five such dislocations into the intra-articular space between the femur and tibia3-6,10-12. In the more common type of horizontal dislocation, direct trauma to the slightly flexed knee causes the patella to rotate in the sagittal plane, about its horizontal axis, into the femorotibial articulation. Thirty-three of the thirty-five dislocations were associated with rupture of the quadriceps tendon3,4,6,10,11. Stimson argued that superior or inferior dislocations of the patella should not be classified as an injury of the knee joint because they are the result of rupture of the patellar ligament or quadriceps tendon. However, in two previously reported cases of intra-articular dislocation of the patella, as in our patient, no rupture or detachment of the quadriceps tendon was found5,11.
Bartlet, D. H.; Gilula, L. A.; and |and |Murphy, W. A.: Superior dislocation of the patella fixed by interlocked osteophytes. A case report and review of the literature. J. Bone and Joint Surg.,58-A: 883-884, Sept. 1976.58-A883  1976 
 
Blackburne, J. S., and |and |Peel, T. E.: A new method of measuring patellar height. J. Bone and Joint Surg.,59-B(2): 241-242, 1977.59-B(2)241  1977 
 
Brady, T. A., and |and |Russel, D.: Interarticular horizontal dislocation of the patella. A case report. J. Bone and Joint Surg.,47-A: 1393-1396, Oct. 1965.47-A1393  1965 
 
Donelson, R. G., and |and |Tomaiuoli, M.: Intra-articular dislocation of the patella. A case report. J. Bone and Joint Surg.,61-A: 615-616, June 1979.61-A615  1979 
 
Fenely, R. C. L.: Intra-articular dislocation of the patella. Report of a case. J. Bone and Joint Surg.,50-B(3): 653-655, 1968.50-B(3)653  1968 
 
Frangakis, E. K.: Intra-articular dislocation of the patella. A case report. J. Bone and Joint Surg.,56-A: 423-424, March 1974.56-A423  1974 
 
Frìden, T.: A case of superior dislocation of the patella. Acta Orthop. Scandinavica,58: 429-430, 1987.58429  1987  [CrossRef]
 
Hanspal, R. S.: Superior dislocation of the patella. Injury,16: 487-488, 1985.16487  1985  [PubMed][CrossRef]
 
Insall, J., and |and |Salvati, E.: Patella position in the normal knee joint. Radiology,101: 101-104, 1971.101101  1971  [PubMed]
 
Midelfart, V.: En sjelden Luxation af Patella. Meddelt of Kompagnikirnrg. Norsk Mag. Laegevidenskaben,4. R. (ii): 588, 1887.4. R. (ii)588  1887 
 
Murakami, Y.: Intra-articular dislocation of the patella. A case report. Clin. Orthop.,171: 137-139, 1982.171137  1982  [PubMed]
 
Rutherford, H.: Downward dislocation of the patella. British J. Surg.,8: 524-526, 1921.8524  1921  [CrossRef]
 
Stimson, L. A.: A Practical Treatise on Fractures and Dislocations, p. 772. New York, Lea Brothers, 1899. 
 
Wilson, J. N. [editor]: Watson-Jones' Fractures and Joint Injuries. Ed. 5, vol. 2, p. 1056. Edinburgh, Churchill Livingstone, 1976. 
 

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Anchor for JumpAnchor for Jump
+FIG. 1 Lateral radiograph of the right knee, made in June 1993, demonstrating horizontal dislocation of the patella in the sagittal plane.
Anchor for JumpAnchor for Jump
+Figs. 2-A, 2-B, and 2-C: Radiographs of the knee, made in July 1993. Fig. 2-A: Anteroposterior radiograph showing hypertrophic changes.
Anchor for JumpAnchor for Jump
+Lateral radiograph showing osteophytes of the patella and femur. There is patella alta according to the Insall-Salvati ratio of 1.35.
Anchor for JumpAnchor for Jump
+2-C Tangential radiograph of the patella.
Anchor for JumpAnchor for Jump
+Figs. 3-A, 3-B, and 3-C: Lateral radiographs made during fluoroscopy without anesthesia. Fig. 3-A: The knee in full extension.
Anchor for JumpAnchor for Jump
+Fig. 3-B: When the quadriceps muscle was contracted, the inferior edge of the patella lay superior to the osteophyte at the margin of the femoral articular surface.
Anchor for JumpAnchor for Jump
+Fig. 3-C: When slight pressure was applied to the patella, the osteophyte at the inferior margin of the patella could be locked posterior to the edge of the femoral osteophyte.

References

Bartlet, D. H.; Gilula, L. A.; and |and |Murphy, W. A.: Superior dislocation of the patella fixed by interlocked osteophytes. A case report and review of the literature. J. Bone and Joint Surg.,58-A: 883-884, Sept. 1976.58-A883  1976 
 
Blackburne, J. S., and |and |Peel, T. E.: A new method of measuring patellar height. J. Bone and Joint Surg.,59-B(2): 241-242, 1977.59-B(2)241  1977 
 
Brady, T. A., and |and |Russel, D.: Interarticular horizontal dislocation of the patella. A case report. J. Bone and Joint Surg.,47-A: 1393-1396, Oct. 1965.47-A1393  1965 
 
Donelson, R. G., and |and |Tomaiuoli, M.: Intra-articular dislocation of the patella. A case report. J. Bone and Joint Surg.,61-A: 615-616, June 1979.61-A615  1979 
 
Fenely, R. C. L.: Intra-articular dislocation of the patella. Report of a case. J. Bone and Joint Surg.,50-B(3): 653-655, 1968.50-B(3)653  1968 
 
Frangakis, E. K.: Intra-articular dislocation of the patella. A case report. J. Bone and Joint Surg.,56-A: 423-424, March 1974.56-A423  1974 
 
Frìden, T.: A case of superior dislocation of the patella. Acta Orthop. Scandinavica,58: 429-430, 1987.58429  1987  [CrossRef]
 
Hanspal, R. S.: Superior dislocation of the patella. Injury,16: 487-488, 1985.16487  1985  [PubMed][CrossRef]
 
Insall, J., and |and |Salvati, E.: Patella position in the normal knee joint. Radiology,101: 101-104, 1971.101101  1971  [PubMed]
 
Midelfart, V.: En sjelden Luxation af Patella. Meddelt of Kompagnikirnrg. Norsk Mag. Laegevidenskaben,4. R. (ii): 588, 1887.4. R. (ii)588  1887 
 
Murakami, Y.: Intra-articular dislocation of the patella. A case report. Clin. Orthop.,171: 137-139, 1982.171137  1982  [PubMed]
 
Rutherford, H.: Downward dislocation of the patella. British J. Surg.,8: 524-526, 1921.8524  1921  [CrossRef]
 
Stimson, L. A.: A Practical Treatise on Fractures and Dislocations, p. 772. New York, Lea Brothers, 1899. 
 
Wilson, J. N. [editor]: Watson-Jones' Fractures and Joint Injuries. Ed. 5, vol. 2, p. 1056. Edinburgh, Churchill Livingstone, 1976. 
 
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