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Extensor mechanism disruption is a rare but devastating complication following total knee replacement. The reported prevalence range from 0.1% for quadriceps tendon rupture to 0.17% to 1.4% for patella tendon rupture. Only partial ruptures can be treated with observation; the majority of full-thickness ruptures require surgical intervention. Primary repair alone has poor success rates. Augmentation or reconstruction with autograft or allograft tendon appears to provide the most satisfying results.
- Weak or lack of active knee extension
Patella tendon rupture
- Occur most commonly in the perioperative period
- Difficult to distinguish from normal pain of surgery
- Clinical exam may reveal a high-riding patella and a palpable soft tissue defect inferior to the patella
Quadriceps tendon rupture
- Often associated with history of injury, such as fall or vigorous activity
- Pain is localized above the patella
- Clinical exam may reveal a palpable soft tissue defect above the patella
- Patella will be in the natural anatomic location
- Lateral radiographs are often diagnostic for patella tendon rupture, showing a high-riding patella (Figure 1)
- Radiographs for quadriceps tendon rupture are oftem normal, although on occasion, the patella may be low-riding
- Normal radiograph, however, does not rule out an extensor mechanism disruption; compare post-injury radiographs with pre-injury radiographs, looking for avulsion fragment above or below the patella
Figure 1. High-riding patella indicative of patella tendon rupture
- Patient is positioned supine on a radiolucent OR table
- General or regional anesthesia may be utilized
- Tourniquet use is recommended but not mandatory
- Leg is prepped and draped in the same fashion as a primary TKA procedure
- Preferable to utilize the existing incision
- If multiple incisions exist, chose the most extensile
- If options exist, midline incision is recommended.
- Medial and lateral full-thickness flaps are elevated for exposure; ruptured extensor mechanism is identified
- Primary repair is always attempted with heavy non-absorbable suture.
Quadriceps Tendon Rupture
Once the quadriceps tendon rupture is identified, fibrous and scar tissue are excised. Likewise, the superior pole of the patella is exposed and debrided down to bleeding bone. Small avulsion fragments should be excised (Figure 2).
Figure 2. Quadriceps tendon rupture
Heavy, non-absorbable suture (#5 ethibond or fiberwire) is utilized for the repair. The suture is weaved through the quadriceps tendon (Krackow Technique) (Figure 3) and then passed through the patella via drill holes (Figure 4). The sutures are then tied over bone bridge with the knee in full extension (Figure 5). The repair is reinforced with #1 ethibond and vicryl suture to repair the retinacular rent (Figure 6).
Figure 3. Suture weaved through quadriceps tendon using Krackow Technique
Figure 4. Parallel drill holes made through patella
Figure 5. Sutures tied over bone bride - note that knee is in full-extension
Figure 6. The repair is reinforced with #1 ethibond suture
Once primary repair is achieved, the allograft tendon is prepared by soaking in antibiotic-impregnated saline solution. The thawed allograft tendon is then prepared on the back table. The calcaneal bone block is excised and discarded (Figure 7). The allograft tendon is draped over the primary repair site (Figure 8), and then the tendon is sutured to the native extensor mechanism to augment the repair (Figure 9). Care should be taken to achieve a stable repair. In addition, it is imperative that the graft is tensioned in full extension to prevent extensor lag.
Figure 7. Achilles tendon graft is prepared by excising calcaneal bone
Figure 8. Achilles tendon allograft draped over primary repair site
Figure 9. Final repair with non-absorbable suture
Patella Tendon Rupture from Patella
Once the patella tendon rupture is identified, fibrous and scar tissue are excised (Figure 10). The inferior pole of the patella is exposed and debrided down to bleeding bone. Small avulsion fragments should be excised.
Figure 10. The patella tendon rupture from inferior pole of patella is identified
Heavy, non-absorbable suture (#5 ethibond or fiberwire) is utilized for the repair. Parallel drill holes are made through the patella using 2.0-mm drill bit (Figure 11). The suture is weaved through the infra-patella tendon (Krackow Technique) and primary repair is completed with knot tied over bone bridge (Figure 12).
Figure 11. Parallel drill holes made through patella
Figure 12. Primary repair is attempted with suture tied over bone bridge
The proximal tibia is prepared to accept the allograft calcaneal bone block. A small oscillating saw is utilized to create a trapezoidal defect in the anterior tibial crest, just below the tibial tubercle (rectangular/trapezoidal cavity 2.5-cm long by 1.5-cm wide by 1-cm deep – osteotome is utilized to lift the unwanted bone out of its bed) (Figure 13). Care should be taken to avoid creating stress risers in the bone to prevent iatrogenic tibia fracture (Figure 14).
Figure 13. Osteotomy is performed below the tibial tubercle using oscillating saw
Figure 14. Final osteotomy made below tibial tubercle
Preparation of the allograft should be performed in the back table. First, the allograft tendon with calcaneal bone block is soaked in antibiotic-impregnated saline solution. Once fully thawed, the calcaneal bone block should be carefully fashioned to fit snugly in the tibial osteotomy site (Figure 15). A “keystone” is created to maximize friction fit and boney contact. Two small fragment screws (3.5 mm) are utilized to “fix” the bone block into the tibia (Figure 16). The screws are angled in different planes to prevent stress-riser in the tibia.
Figure 15. The calcaneal bone is prepared to snugly fit into ostetomy site
Figure 16. Two 3.5-mm screws are utilized to stabilize allograft into the tibia
The Achilles tendon is draped over the native patella tendon, patella and quadriceps tendon. The allograft tendon is then sutured the native extensor mechanism (Figure 17).
Figure 17. Final repair using non-absorbable suture
Patella Tendon Rupture from Tibial Tubercle
Similar to the treatment of patella tendon rupture from the inferior pole of the patella, initially, the patella tendon rupture is identified (Figure 18). Fibrous scar and boney avulsion fragments are excised. Primary repair of patella tendon is always attempted. Heavy, non-absorbable suture (#5 ethibond or fiberwire) is weaved through the infra-patella tendon using the Krackow Technique (Figure 19).
Figure 18. Patella tendon avulsion from tibial tubercle is identified
Figure 19. Non-absorble suture is weaved through the tendon
Primary repair is performed through drill holes in the tibial tubercle. A small drill (1.6 mm or 2.0 mm) and suture passer are utilized to pass the suture through the bone – tibial tubercle (Figure 20). The repair is reinforced with #1 ethibond to repair the retinacular rent (Figure 21). The repair is tensioned with the knee in extension.
Figure 20. Primary repair is performed through drill holes in the tibial tubercle
Figure 21. Repair is reinforced with #1 ethibond
The proximal tibia is prepared to accept the allograft calcaneal bone block (see above). A small oscillating saw is utilized to create a trapezoidal defect in the anterior tibial crest just below the tibial tubercle (rectangular/trapezoidal cavity 2.5-cm-long by 1.5-cm-wide by 1-cm-deep – osteotome is utilized to lift the unwanted bone out of its bed). Care should be taken to avoid creating stress risers in the bone to prevent iatrogenic tibia fracture. (see above)
Preparation of the allograft should be performed in the back table. First, the allograft tendon with calcaneal bone block is soaked antibiotic-impregnated saline solution. Once fully thawed, the calcaneal bone block should be carefully fashioned to fit snugly in the tibial osteotomy site. A “keystone” is created to maximize friction fit and boney contact. Two small fragment screws (3.5 mm) are utilized to “fix” the bone block into the tibia. The screws are angled in different planes to prevent stress-riser in the tibia. (Figures 22, 23)
Figure 22. AP radiographs of fixation screws; different angles are chosen to prevent fracture
Figure 23. Lateral radiographs of allograft fixed to proximal tibia
The Achilles tendon is then draped over the anterior tibia and patella. (see above) The allograft tendon is then sutured to the native extensor mechanism to augment the repair (Figure 24). Care should be taken to achieve stable repair. In addition, it is imperative that the graft is tensioned in full extension to prevent extensor lag.
Figure 24. Final repair utilizing non-absorbable suture
Pearls and Pitfalls
- Always attempt primary tendon repair in conjunction with allograft tissue reconstruction (although primary repair alone often lead to failure)
- ORIF of a patella fragment should be avoided. Most fractures that are repaired will go onto non-union, especially if the patella have been previously resurfaced
- Tension the extensor mechanism reconstruction in full extension to prevent extensor lag
- Initial immobilization is important to protect repair.
- Most patient will obtain final flexion greater than 90 degrees without need for MUA
- The knee is placed in a knee immobilizer after surgery and then kept in full-extension for 3 weeks
- Patient is allowed touch-down weight bearing for the first 3 weeks post-op
- At the 3-week mark, the patient is allowed to work with a therapis; gradual range of motion is initiated at this time.
- Hinge-knee brace is applied and is unlocked with the flexion stop set at 60 degrees.
- Gradual increase in flexion (10 degree per week) is allowed until 90 degrees of flexion is achieved.
- Patient is graduated to 50% weight-bearing at 4 weeks and then progressed to full-weight bearing at 6 weeks.
- Most patients regain pre-injury flexion without the need for manipulation under anesthesia (Figures 25, 26).
Figure 25. Flexion
Figure 26. Extension
Extensor mechanism disruption is a devastating injury with few options. Reconstruction with allograft tendon appears to be most viable treatment strategy. However, failures of repair do still occur. mid-term follow-up revealed that (_%) fail or “stretch” out and lead to weakness and significant extensor lag.
- Failure of graft
- Extensor lag
- Weakness (difficulty with stairs)
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Lynch A, Rorabeck C, Bourne R. Extensor mechanism complications following total knee arthroplasty. J Arthroplasty 1987;2(2):135-40
Rand J. Extensor mechanism complications following total knee arthroplasty. J Knee Surg 2003;16(4):224-8
Burnett S, Berger R, Paprosky W, Della Valle C, Jacobs J, Rosenberg A. Extensor mechanism allograft reconstruction after total knee arthroplasty. A comparison of two techniques. J Bone Joint Surg Am 2004;86-A(12):2694-9