Tkr

Basics of total knee replacement

1. Prepared by Dr . Md. Ashiqur Rahman Phase-B Resident DMCH Basics of Total Knee Replacement

2. TKR First performed in 1968 Initial experience is bad. Significant advances have occurred over 50 years One of the most successful procedures More than 600,000 performed in USA annually

3. TKR Overview Anatomy of the Knee joint Common conditions requiring TKR Evolution Of TKR Total Knee Replacement Our experience

4. TKR

5. TKR Recommended pre-operative radiographs: Standing full length AP from hip to ankle. Lateral Skyline view

6. Constraints : Definition : The ability of a prosthesis to provide varus -valgus and flexion-extension stability in the face of ligamentous laxity or bone loss. Importance: In the setting of ligamentous laxity or severe bone loss, standard cruciate-retaining or posterior-stabilized implants may not provide stability.

7. 1a.Constrained Hinged prosthesis

8. 1a.Constrained Hinged TKR prosthesis: Most constraint prosthesis are linked with linked femoral and tibial components (Hinged). Indications: Resection of tumor. Massive bone loss in the setting of neuropathic joint. Global ligamentous laxity. Hyperextension laxity.

9. 1b.Constrained non-hinged prosthesis:

10. 1b.Constrained Non-Hinged TKR prosthesis: Constrained prosthesis without axle connecting tibial & femoral components(Non hinged). Indications: LCL attenuation or deficiency. MCL attenuation or deficiency. Flexion gap laxity. Moderate loss in the setting of neuropathic arthropathy .

11. 2a.Cruciate Retaining: Minimally constrained prosthesis that depends on an intact PCL to provide stability in flexion. Indications: Arthritis with minimal bone loss, minimal soft tissue laxity, and an intact PCL. Varus deformity < 10 degrees Valgus deformity > 15 degrees

12. 2b.Posterior stabilizing(PS)/ Cruc . substituting Slightly more constraint prosthesis that requires sacrifice of PCL. Femoral component contains a cam that engages the tibial polyethylene post during flexion. Polyethylene inserts are more congruent and deeply dished. Resection of PCL increases the flexion gap in relation to extension gap so posterior must be matched to avoid flexion-extension mismatch.

13. 2.Posterior stabilizing(PS)

14. 2b.Posterior stabilized(PS) TKR Indications: Previous patellectomy (weak extensor mechanism) Inflammatory arthritis. Deficient or absent PCL.

15. 2c.Mobile Bearing prosthesis Minimally constrained prosthesis where the polyethylene can rotate on the tibial baseplate. PCL is removed at time of surgery. Indications: Young, active patients(relative indication)

16. 3 .Uni-condylar TKR

17. 3 .Uni-Condylar TKR These prostheses replace the articular surface of either the medial or the lateral femoral condyle and the adjacent tibial plateau surface. Advantages: Allows easy revision to a tri-compartmental prosthesis later on. Preservation of the proprioceptive function of the ligaments. Shorter rehabilitation time. Greater average post-op range of motion.

18. 4 .Total condylar prosthesis

19. 4 .Total condylar prosthesis Disadvantages: Tendency to subluxate posteriorly in flexion if flexion gap is larger than the extension gap. Lack of femoral roll back. Smaller range of flexion if the PCL was not functioning.

20. Foot notes(Campbell’s) Many surgeons advocate use of PCL retaining prostheses for mild deformity. And PCL substituting design for more severe deformity.

21. Mechanical axis of the lower limb is a straight line from the center of the femoral head to the center of the ankle.

22. TKR bone cuts For distal femur(05 cuts): Distal femoral Anterior femoral Posterior femoral Anterior chamfer Posterior chmafer B. For Tibia(01 cut ) C. For patella(01 cut)

23. Figure shows a 5-in-1 cutting block with anterior femoral cut (line 1), posterior femoral cut (line 2), posterior chamfer cut (line 3), anterior chamfer cut (line 4), and distal femoral cut (line 5). Of note, most TKA systems have a 4-in-1 cutting block and the distal femoral cut is made separately.

24. Here are 7 bone cuts in a total knee replacement . The posterior condylar cut determines the flexion gap. Flexion instability in PS knees arises because of an enlarged flexion gap (excessive posterior condylar resection, or increased tibial slope), allowing anterior tibial translation, which is pathognomonic. There will not be posterior subluxation because of the cam-post design. Symptoms include the sensation of instability without giving way, especially with stair climbing, recurrent knee effusions, and diffuse knee pain. Signs include anterior tibial translation at 90° flexion, tenderness at multiple sites (including pes anserinus , peripatellar , posterior hamstrings), and effusion. Revision surgery is indicated for symptomatic patients. Review more high-yield topics about TKA Instability on the most recent episode of The Orthobullets Podcast. Listen wherever you get your

25. Illustration shows restoration of the posterior condylar offset (line A) with the femoral component (line B).

26. Proximal Tibia is cut in neutral alignment, previously it was practiced to cut in 3 degrees varus . Ideally femoral articulation should have an angulation of 3 to 7 degrees of valgus, in early TKR designs, proximal tibia was cut upto 3 degrees of varus . Which meant that distal femoral cut was made in 7-9 degrees of valgus. If the proximal tibia cut is to be made in neutral (this is now standard), then femoral cut guide is set for the appropriate right or left valgus angulation of + 5 to 7 degrees.

27. Depth of the femoral component cut is usually 8-9mm, often surgeons will add, 1-2mm to this length; so a total of 10 to 12 mm of total length is cut from the distal femur. However there are issues like posterior stabilized or cruciate retaining TKR, proximal tibial slope of 3 degrees of internal or external rotation. Which is much less understood .

28. Medial para-patellar approach

29. Medial para-patellar approach Overview : Most commonly completed through a straight midline incision. Advantages: Familiar for most orthopedic surgeons. Excellent exposure even in most challenging cases. Disadvantages: Possible failure of medial capsular repair. Development of lateral patellar subluxation. Access to lateral retinaculum less distinct. May jeopardize lateral retinaculum if lateral release is performed.

30. Post. Op. Rehabilitation Observed 24 hours in high dependency ward. Good hydration & Analgesia. Cryotherapy. Drains removed in 24 hours. Rapid post. Operative mobilization. Range of motion exercises CPM Muscle strengthening exercises Wt. bearing allowed on 2 nd post op day. Discharged in 5 – 15 days.

31. Complications Thromboembolism Infection Patello - femoral complications Neurovascular complications Peri -prosthetic fractures Aseptic loosening Arthro -fibrosis

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