ABSTRACT OF THE WEEK

Journal of the American Animal Hospital Association
Volume 52 | Issue 3 (2016 May-Jun)

Outcome Following Surgical Correction of Grade 4 Medial Patellar Luxation in Dogs: 47 Stifles (2001-2012).

J Am Anim Hosp Assoc. 2016 May-Jun;52(3):162-9.

Eric C Hans¹, Sharon C Kerwin², Alan C Elliott³, Ryan Butler⁴, W Brian Saunders⁵, Don A Hulse⁶

¹ From the Department of Veterinary Small Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX (E.C.H., S.C.K., W.B.S., D.A.H.); Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS (R.B.); and Department of Statistical Science, Southern Methodist University, Dallas, TX (A.C.E.).; ² From the Department of Veterinary Small Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX (E.C.H., S.C.K., W.B.S., D.A.H.); Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS (R.B.); and Department of Statistical Science, Southern Methodist University, Dallas, TX (A.C.E.).; ³ From the Department of Veterinary Small Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX (E.C.H., S.C.K., W.B.S., D.A.H.); Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS (R.B.); and Department of Statistical Science, Southern Methodist University, Dallas, TX (A.C.E.).; ⁴ From the Department of Veterinary Small Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX (E.C.H., S.C.K., W.B.S., D.A.H.); Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS (R.B.); and Department of Statistical Science, Southern Methodist University, Dallas, TX (A.C.E.).; ⁵ From the Department of Veterinary Small Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX (E.C.H., S.C.K., W.B.S., D.A.H.); Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS (R.B.); and Department of Statistical Science, Southern Methodist University, Dallas, TX (A.C.E.).; ⁶ From the Department of Veterinary Small Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX (E.C.H., S.C.K., W.B.S., D.A.H.); Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS (R.B.); and Department of Statistical Science, Southern Methodist University, Dallas, TX (A.C.E.).

Abstract

Grade 4/4 medial patellar luxation (MPL) is a complex disease of the canine stifle that often requires surgical realignment of the patella to resolve clinical lameness. Outcome following surgery remains poorly described. Medical records were retrospectively reviewed for surgical correction of grade 4 MPL. Signalment and exam findings, surgical procedures performed, complications, and clinical outcome were reported. Data was statistically analyzed for association with major complication occurrence and unacceptable function following surgery. Forty-seven stifles from 41 dogs were included. The surgical procedures most frequently utilized for patellar realignment were the combination of femoral trochleoplasty, tibial tuberosity transposition, and joint capsule modification. Median in-hospital veterinary examination was performed at 69 days (range 30-179 days) following surgery. Full function was reported for 42.6% of cases (n=20). Acceptable function was reported for 40.4% of cases (n=19). Unacceptable function was reported for 17% of cases (n=8). The overall complication rate was 25.5% (n=12), with revision surgery for major complications required in 12.8% of cases (n=6). Corrective osteotomies were associated with major complications (P < 0.001). In general, pelvic limb function improves following surgical correction of grade 4 MPL; however, a return to full function should be considered guarded.

Companion Notes

Retrospective report on outcomes following surgical correction of grade 4 medial patellar luxation in 41 dogs (47 stifles)

Introduction on medial patellar luxation (MPL) in the dog

- disorder is often developmental but can be acquired after trauma or surgery

- commonly associated with the following:

- quadriceps displacement

- shallow femoral trochlear groove

- torsion of tibial tuberosity

- patella alta

- common clinical signs include the following:

- stifle discomfort

- lameness, intermittent or persistent

- severity often characterized by a grading scheme from 1-4 first devised by Putman

(Putman RW: Patellar luxation in the dog [master's thesis]. Ontario, Canada:

University of Guelph; 1968)

- later adapted by Singleton and others

(Singleton WB. The surgical correction of stifle deformities in the dog. J

Small Anim Pract 1969:10;59-69)

- grade 4/4 luxation is most severe form

- permanent luxation that can’t be manually reduced

- the below have also been included in some definitions of grade 4/4

- internal rotation of tibial tuberosity

- shallow or absent trochlea of femur

- displacement of quadriceps muscle group

- grade 4 also associated with femoral and tibial angular limb deformity

- these anatomic changes impair stifle extension and often result in:

- bow legged posture

- severe hindlimb lameness

- in 1 report

- it’s associated with greater risk of rupture of cranial cruciate ligament

- little in literature on outcome of grade 4 as compared to other grades

- in 4 studies surgical outcome was poor to excellent

- studies used very small cohorts of 1-16 cases

- 1 report suggested age ≤ 1 year essential for a successful outcome

- multiple recent studies emphasize doing corrective osteotomies

- notably distal femoral osteotomy to correct femoral varus

- particularly in large breed dogs

- these reports generally did not include grade 4 MPL

- prognosis for surgery of grade 4 MPL is considered guarded

Study design

- study population: dogs seen at 2 specialty surgical centers from 01-12

- dogs had grade 4 MPL confirmed intra-operatively

- also had a follow-up in-hospital exam by veterinarian > 4 weeks postop

- grade 4 MPL: continually luxated and can’t be manually reduced

- history & signalment

- Yorkshire terrier, 6 cases; chihuahua, 5; pomeranian, 5

- median age at surgery: 36 months of age with a range of 6-192

- median weight at time of surgery: 5 kg with a range of 1.2-44.9

- grade 4 MPL considered developmental, 38 of the 41 dogs

- grade 4 acquired MPL, 3 dogs based on history of hindlimb trauma

- bilateral MPL, 34 dogs (14 specifically with bilateral grade 4 MPL)

- procedure: records retrospectively reviewed

- surgery done by board-certified surgeon or resident under direct supervision

- all techniques used were chosen at discretion of operating surgeon

- medial or lateral parapatellar approach to stifle then stifle arthrotomy

- if there was a concomitant cranial cruciate ligament rupture (CrCl)

- lateral fabello-tibial suture technique

- bone anchor suture system

(FASTak Suture Anchor; Arthrex Vet Systems, Naples, FL)

- femoral trochlear depth assessed and deepened when appropriate

- either wedge or block recession technique

- or trochlear sulcoplasty

- tibial tuberosity transposition (TTT) in select cases

- stabilized with 1 of the following

- Kirschner wires (K-wire)

- intramedullary pins

- tension band added in select cases

- soft tissue joint capsule modifications as needed included:

- capsulectomy

- imbrication

- desmotomy

- rectus femoris release performed in select cases

- if angular limb deformity of femur or tibia identified on preoperatively

- if considered clinically significant, corrective osteotomy done

Results

- efficacy (median in-hospital veterinary exam performed 69 days postop)

- full function, 42.6% of cases

- acceptable function, 40.4% of cases

- unacceptable function, 17% of cases

- overall complication rate: 25.5% (12 stifles) (none were catastrophic)

- revision surgery for major complications, 12.8% of cases (6 cases)

- clinically significant persistent patellar luxation, 2

- incisional dehiscence

- implant failure/migration

- incorrect osteotomy alignment

- tibial crest avulsion fracture

- corrective osteotomies significantly associated with major complications

- major complication 157.1 times more likely when performed than when not

- surgical procedures for patellar realignment included the following:

- combination of the following was most common, 59.6%

- femoral trochleoplasty

- tibial tuberosity transposition

- joint capsule modification

- combination of the following was next most common, 14.9%

- femoral trochleoplasty

- tibial tuberosity transposition

- joint capsule modification

- corrective osteotomy

- joint capsulectomy/imbrication, 45 joints

- TTT, 42

- desmotomy, 38

- wedge recession trochleoplasty, 23

- block recession trochleoplasty, 14

- anti-rotational suture, 10

- trochlear sulcoplasty, 8

- rectus femoris release, 8

- corrective osteotomy, 8

- concomitant CrCL rupture, 5

- lateral fabello-tibial suture technique, 3 or bone anchor suture system, 2

“The short-term clinical outcome following surgery is often positive; however, the prognosis for full function should be considered guarded.”

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