Ligaments and Tendons

Our research and treatment have focused on repair and replacement of the ACL, PCL and reconstruction of the posterolateral corner. 

Our ligament repair technique was developed by Dr. Stone in the early 1990s.  The technique focused on partial ligament tears close to the bony insertion.  By microfracturing the bone, marrow stem cells were released to stimulate healing.  A novel suture technique was then used to place stitches in the torn fibers of the anterior or posterior cruciate ligament and secure it to the bone with a suture anchor.  (see ACL repair page).   Over the years the indications for ligament repair were tightened to only include partial tears right at the bony insertion.

Ligament replacement always involved using the patient's own patellar tendon called bone-patella-tendon bone until approximately 2005.  Once adequate sterilization procedures were introduced to tissue banking Stone  then exclusively used allograft (donor) bone-patella tendon-bone tissue.   The results have been extremely successful and have eliminated the anterior knee pain and weakness from harvesting the patients own tissue.

Since young healthy human tissue is always in short supply,  Dr. Stone initiated a program in 1996 to solve the rejection problem when animal tissues are transplanted into humans.  Animal tissues are plentiful, young strong and healthy every time and can be sterilized.  The cause of rejection when live animal organs were transplanted into people had been identified by Dr. Uri Galili  as a specific carbohydrate called the Gal eiptope.

Removing the offending gal epitope

Dr. Stone contacted Dr.Galili and the New York Blood Center where a trial of a specific enzyme that removed the gal epitope was being used to change type A and B blood to type O blood for universal donation. Since the carbohydrate that attaches to blood is similar to the carbohydrate in tissues, Dr. Stone eventually obtained this enzyme and designed a process for permeating ligaments, cartilage, meniscus, and bone. After successfully removing nearly all of the gal carbohydrate from tissues in bench testing with Tom Turek and Uri Galili, they began testing in old world primates which were the only non-human animal that would demonstrate a tissue rejection response when animal tissue was transferred. 

These primate studies demonstrated efficacy removing the antigens that cause rejection when animal tissues are transplanted to people. Tissues tested included the meniscus, the bone-patellar-bone tendon, cortical and cancellous bone, soft tissue plugs and articular cartilage. This work led to multiple publications in the Journal of Tissue Transplantation documenting animal tissue could be transplanted in humans if the antigens were removed and documenting a specific technique for antigen removal. Multiple patents were issued to the team around this field. After successful primate testing, a human clinical trial, of bone-patellar-bone ACL replacement was designed and carried out at The Stone Clinic initiated in 2003 demonstrating the ligament could be successfully and safely implanted and would be a sustained treatment in patients. The success of this human clinical trial was accepted by the FDA and a wide U.S. clinical trial was approved up to 10 sites for 326 patients. This trial has yet to be initiated. In the meantime, a European clinical trial comparing xenograft tissue to allograft tissue was initiated and successfully completed with over a 90% success rate with an expected approval of the ligament to be sold in Europe by 2014. 

Successful research, bringing new ideas from the clinic to the lab and then back to the clinic to help solve challenging problems in orthopaedics defines the programs Dr. Stone has committed to and successfully carried out over the last three decades.

Surgical Technique Videos: ACL, PCL, Postero-Lateral Corner


Cell-seeded allografts for repairing ruptures of the Anterior Cruciate Ligament


We hypothesize that treatment of ACL ruptures with cell-seeded bone-tendon-bone (BTB) allograft could accelerate the early healing process and consequently lead to increased mechanical strength compared with ACL reconstruction using unseeded BTB allograft.


Sheep will undergo ACL reconstruction using a bone–patellar tendon–bone allograft. The ACL reconstruction will be performed with either a standard allograft (ACLR; control) or using the same allograft seeded with cells (ACLR+C; experimental).


Anterior Cruciate Ligament Reconstruction with a Porcine Xenograft: A Serologic, Histologic, and Biomechanical Study in Primates. Stone KR, Walgenbach AW, Turek TJ, Somers DL, Wicomb W, Galili U. Arthroscopy: The Journal of Arthroscopic and Related Surgery. April 2007;23:411-419.

Replacement of Human Anterior Cruciate Ligaments with Pig Ligaments: A Model for Anti-NonGal Antibody Response in Long-Term Xenotransplantation. Stone KR, Abdel-Motal UM, Walgenbach AW, Turek TJ, Galili U. Transplantation. January 2007;83:211-219. 

The Excruciating Cruciate. Stone KR, Potts CR. Men's Fitness, January 1992. 

Changes in Knee Stability After Bone-Patellar Tendon-Bone Graft Anterior Cruciate Ligament Reconstruction and Iliotibial Band Tenodesis. Paschal SO, Stone KR, Steadman JR. The American Journal of Knee Surgery, 4(4):173-185, Fall 1991. 

The Knee Joint Anterior Cruciate Ligament: Injury and Prevention. Stone KR. The Professional Skier, 3: 48-49, Winter 1989. 

Ligament and Tendon Oxygenation Measurements Using Polarographic Oxygen Sensors. Stone KR, Bowman HF, Boland A, Steadman JR. Arthroscopy: The Journal of Arthroscopic and Related Surgery, 3(3):187-195, 1987.


"Pig Articular Cartilage as Xenograft." (NIH-SBIR) Award # 1R43 AR45321-01, 1998. 


"Proteoglycan-Reduced Soft Tissue Xenografts." US Patent 6,455,309. Issued September 24, 2002. 

"Soft Tissue Xenografts." US Patent 6,758,865 B1. Issued July 6, 2004.

"Anterior Cruciate Ligament Xenografts." US Patent 6,402,783. Issued June 11, 2002. 

"Method of Prepairng Xenograft Heart Valves." US Patent 6,383,732. Issued May 7, 2002. 

"Proteoglycan-Reduced Soft Tissue Xenografts." US Patent 6,267,786. Issued July 31, 2001. 

"Aldehyde and Glycosidase-Treated Soft and Bone Tissue Xenografts." US Patent 6,231,608. Issued May 15, 2001. 

"Anterior Cruciate Ligament Xenografts." US Patent # 6,210,440. Issued April 3, 2001

"Anterior Cruciate Ligament Xenografts." US Patent # 6,110,206. Issued August 29, 2000. 

"Anterior Cruciate Ligament Heterograft." US Patent # 6,063,120. Issued May 16, 2000. 

"Anterior Cruciate Ligament Heterograft." US Patent # 5,902,338. Issued May 11, 1999. 

"Anterior Cruciate Ligament Repair Method." US Patent # 5,702,422. Issued December 30, 1997.

"Prosthetic Ligaments." US Patent # 5,263,984. Issued November 23, 1993.