Physiofobi

ACL Reconstruction with the use of semitendinosus tendon autograft: What happens to the donor site? 🦵

👉 The anterior cruciate ligament (ACL) is the most frequently injured ligament of the knee, with an estimated 400,000 ACL reconstructions (ACLR) performed each year worldwide.1 In Australia, ~90% of ACLRs use a semitendinosus (ST) tendon autograft because of the mechanical strength of the graft, ease of surgical access, and perceived minimal donor site morbidity. (https://pubmed.ncbi.nlm.nih.gov/30582107/, https://pubmed.ncbi.nlm.nih.gov/26391988/).

👉Following harvesting for graft, ST may undergo a regenerative process known as the “lizard tail phenomenon”, re‐attaching neo‐tendon to the proximomedial tibia below the knee joint line. (https://pubmed.ncbi.nlm.nih.gov/1558254/) However, ~30% of ACLR patients experience no regeneration of harvested ST tendon. (https://pubmed.ncbi.nlm.nih.gov/25548149/)

⛹️‍♂️🤸 Most individuals return to physical activity after ACLR (https://pubmed.ncbi.nlm.nih.gov/31189037/), but with long‐term deficits in knee flexor and internal rotator strength, (https://pubmed.ncbi.nlm.nih.gov/27432052/, https://pubmed.ncbi.nlm.nih.gov/31030253/) presumably due to postoperative morbidity of harvested muscle. (https://pubmed.ncbi.nlm.nih.gov/27432052/)

🤕 These strength deficits following ACLR may contribute to the well‐documented elevated risk of secondary ACL rupture, (https://pubmed.ncbi.nlm.nih.gov/22869626/, https://pubmed.ncbi.nlm.nih.gov/22184280/, https://pubmed.ncbi.nlm.nih.gov/31730379/) primary
hamstring strain injury, (https://pubmed.ncbi.nlm.nih.gov/32299793/, https://pubmed.ncbi.nlm.nih.gov/34709603/) and early onset knee osteoarthritis (https://pubmed.ncbi.nlm.nih.gov/30887068/)

👉 The ST is a critical antagonist of frontal/transverse plane knee moments, recruited to support the knee during high‐risk tasks such as landing and changing of direction. (https://pubmed.ncbi.nlm.nih.gov/12544645/, https://pubmed.ncbi.nlm.nih.gov/28029798/, https://pubmed.ncbi.nlm.nih.gov/11522305/)

Following tendon harvesting for ACLR, ST experiences
▶︎ atrophy, (https://pubmed.ncbi.nlm.nih.gov/27432052/, https://pubmed.ncbi.nlm.nih.gov/31030253/)
▶︎ retraction, (https://pubmed.ncbi.nlm.nih.gov/34471958/)
▶︎ shape change, (https://pubmed.ncbi.nlm.nih.gov/35434842/)
▶︎ fatty infiltration (https://pubmed.ncbi.nlm.nih.gov/22810397/),and
▶︎ impaired activation (https://pubmed.ncbi.nlm.nih.gov/19684295/)

👉Compared to uninjured contralateral limbs, regenerated ST tendons have been reported to insert more proximally and medially on the tibia following ACLR, or within the popliteal fascia. (https://pubmed.ncbi.nlm.nih.gov/25548149/)

👉Altered ST morphology and distal tendon insertion following ACLR may impair torque generating capacity of the hamstrings through altered muscle force‐generating capacity, moment‐arm, or both. (https://pubmed.ncbi.nlm.nih.gov/33680834/)

📘 According to du Moulin and colleagues, compared to uninjured contralateral limbs, ACLR limbs with tendon regeneration (n = 7) had minor reductions in knee flexion (5.80% [95% confidence interval (CI) = 3.97–7.62]) and internal rotation (4.92% [95% CI = 2.77–7.07]) moment arms. But coupled with muscle morphology, ACLR limbs with tendon regeneration had substantial deficits in knee flexion(19.32% [95% CI = 18.35–20.28]) and internal rotation (15.49% [95% CI = 14.56–16.41]) torques compared to uninjured contralateral limbs. https://onlinelibrary.wiley.com/doi/full/10.1002/jor.25814

👉 In addition to ST atrophy/retraction, potential compensatory hypertrophic changes in other synergistic hamstring muscles are possible, (https://pubmed.ncbi.nlm.nih.gov/27432052/, https://pubmed.ncbi.nlm.nih.gov/31030253/) which may mitigate reductions in knee flexion torque generating capacity.

Illustration: Diagram of the hamstring muscles. BF biceps femoris muscle, ST semitendinosus muscle, SM semimembranosus muscle, CT common tendon, CT(ft) free-tendon part of the common tendon. SN sciatic nerve, IT ischial tuberosity, FH fibular head, FT fat tissue in the space between the BF and ST/SM muscles, (*) Popliteal vessels and nerve are interposed between the BF and ST/SM muscles. https://link.springer.com/article/10.1007/s00256-019-03208-x

Nachdem bekannt geworden ist, dass bis zu 50% der vorderen Kreuzbandrupturen eine Spontanheilung aufweisen, entwickelten australische Forscher das "Cross Bracing Protocol", wo VKB-Rupturen konservativ mit einer Orthese behandelt wurden - mit erstaunlichen Ergebnissen!