History
Patellar Tendon
Semi-Tendinosus
Issues in Hamstring Grafts
Allograft
Quads tendon
Synthetic





History

The type of graft that the surgeon chooses for ACL reconstruction has evolved over the past few years. In the later 80s the common graft choice was patellar tendon autograft. There were a few people using semi-tendinosis, such as Peter Fowler. However even Peter was not so sure of its strength since he used a LAD (ligament augmentation device)

In the light of harvest site morbidity and post op stiffness associated with the patellar tendon graft, many surgeons began to look at other choices, semi- tendinosis, allograft, and synthetics. My choice as an alternative was Gore-Tex. My initial experience was unsatisfactory. However, with the second generation graft, improved surgical technique, and better patient selection, the results improved.

In the 90s using the aggressive post-op rehab program diminished the problems associated with the patellar tendon.

Allograft was another choice that avoided the problem of harvest site morbidity. Since we in Canada had a reasonable synthetic, there was no demand for the allograft. This did become a popular alternative to the autograft and reduced the harvest site morbidity, as well as the operative time.

There was renewed interest in the mid 90s, with the semi-tendinosis, using the multiple bundle technique and improved fixation with the endo-button. The multiple bundles made the graft stronger and stiffer. The endo button made the procedure endoscopic, and eliminated the need for the second incision.

The latest twist in fixation is to use an interference fit screw to fixate the graft at the tunnel entrance. This produces a graft construct that is strong, short, and stiff. It means that now the surgeon just has to learn one technique for drilling the tunnels and he can chose whatever graft he wishes, hamstring, patellar tendon, or allograft.

Table 1 Evolution of my graft choice since 1990









Patellar Tendon


Advantages

• Early bone to bone healing at 6 weeks
  
• Consistent size and shape of graft
  
  
  

Disadvantages

• Harvest site morbidity
  
• Patellar tendinitis
  
• Anterior knee pain
  
• Patellar stiffness and lack of motion, leading to increase patello-femoral joint compression and late chondromalacia of the patella.
  
• Late patellar fracture
  
• Loss of range of motion
  
  
  

Semi-Tendinosus


Advantages

• 4 bundle graft is stronger and stiffer than the patellar tendon
  
  
  

Grafts courtesy Dr. Steve Howell


Disadvantages

• Graft fixation to bone, staples, endo-button.
  
• The graft harvest can be difficult, with cutting the tendons off short
  
• Longer time for graft healing to bone 10 12 weeks
  
  
  

Issues in Hamstring Grafts

• Graft Strength
  
• Noyes - one strand is only 70% of the strength of the ACL
  
• Sepaga - The semi-t and gracilis composite graft is equal to an 11 mm patellar tendon graft
  
• Marder and Larson feel that the 4 bundle tensioned equally is 250 % the strength of the normal ACL
  
• Howell - 4 bundles 4,300 N cf 1750 N for ACL
  
• Graft Stiffness
  
• 4 bundle semi-t and gracilis 2X Patellar tendon and 3X normal ACL
  
• Graft Fixation
  
• Endo button and tying over periosteal buttons may be too weak and elastic. Moving the fixation closer to the tunnel entrance improved results - Fu Pinczewski showed no difference in outcome with interference screw fixation in semi-t and patellar tendon, except for harvest site morbidity
  
• Pull out strength studies by several authors, Caborn, Weiler, Paulos, showed adequate pullout strength for the interference screw soft tissue fixation. ( all above 400 N )
  
• Graft Healing
  
• Semi-t takes 10-12 weeks to heal to bone
  
• Donor site Morbidity
  
• Semi-t has 3-21% of anterior knee pain - less than patellar tendon
  
• Muscle strength - Lipsome found there was no demonstrable weakness after hamstring harvest.
  
• Early aggressive rehab
  
• Aligetti and Marder showed there was no difference in outcome with early aggressive rehab. Therefore the semi-t has been shown to withstand aggressive rehab, and probably early return to sports. ( as shown by Howell)
  
  
  

Allograft

Advantages

• No harvest site morbidity
  
  
  

Disadvantages

• Risk of disease transmission
  
• Weaken graft, if radiated
  
• Older donor weaker graft
  
• Longer graft to bone incorporation time
  
• Not readily available
  
• Expensive
  
  
  

Quads tendon

Advantages

• Less harvest site morbidity
  
• Larger cross sectional area of graft
  
  
  

Disadvantages

• Only bone block on one end of graft
  
  
  

Synthetic

Advantages

• No harvest site morbidity
  
• No disease transmission
  
  
  

Disadvantages

• Higher rate of late graft failure
  
• Increased risk of late infection
  
• Expensive
  
• Compression and late chondromalacia of the patella
  
• Late patellar fracture
  
• Loss of range of motion