Hypermobility, ACL reconstruction & shoulder instability: a clinical, mechanical and histological analysis
Akhtar, Muhammad Adeel
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Joint movements are essential for the function of human body during the activities of daily living and sports. The movement of human joints varies from normal to those which have an increased range of joint movement (gymnasts) to those with extreme disabling laxity in patients with a connective tissue disorder (Ehlers Danlos Syndrome). “Hypermobility" is most commonly used to describe excessive movement. Hypermobility was assessed by using the current criteria of the Beighton score for signs and the Brighton criteria for symptoms of hypermobility in a group of orthopaedic patients attending the specialist knee and shoulder injury clinics. The Beighton score was found to be higher in patients attending for primary ACL reconstruction (mean 2.9, p = 0.002) and revision ACL reconstruction (mean 4, p < 0.001) when compared with the control group. Hypermobility was a risk factor for the failure of ACL reconstruction (30% vs 0%). The mean Beighton score was higher in both the primary shoulder dislocation group (mean difference 1.8, p=0.001) and the recurrent shoulder dislocation group (mean difference 1.4, p=0.004). Bone defects were studied on the CT scan following shoulder dislocations. There was no correlation between hypermobility and the bone defects. The bone defect was a risk factor for recurrent shoulder instability (48% vs 16%). A material testing system was used to assess the tissue laxity of discarded hamstring tendon and shoulder capsule obtained during stabilisation procedures. The mean gradient of slope for both tendon and capsule graphs was 23.8 (range 3.08-52.63). The tissue laxity was compared to the Beighton score, however no correlation was detected between the Beighton score and the gradient of the tissue laxity. An electronic goniometer was used to measure the angle of the MCP joint of the little finger, whilst a force plate system simultaneously measured the force required to hyperextend the MCP joint. The little finger MCP joints of each hand were assessed in this manner in a group of patients undergoing primary ACL reconstruction or open shoulder stabilization. The mean force required to produce the 40 degrees angle at the little finger MCP joint was 0.04 kg with a range from 0-0.11 kg. There was a positive correlation between the gradient of tissue laxity and the force required to produce 40 degrees angle at the little finger of the dominant hand. The expression of Collagen V and Small leucine rich proteoglycans (Decorin and Biglycan) was studied in the skin, hamstring tendon and shoulder capsule of the patients described above attending with shoulder or knee instability. These patients had different levels of hypermobility (as assessed by the Beighton score) and symptoms of hypermobility (as assessed by the Brighton criteria to diagnose Benign Joint Hypermobility Syndrome). The weaker tendon group was found to have a lower mean Beighton score, while the weaker skin group had a higher mean Beighton score. Collagen V expression was higher in the skin dermal papillae of the weaker group. The Beighton Scores were higher in patients with ACL and shoulder injuries. Hypermobility was a risk factor for the failure of ACL reconstruction. There was no correlation between hypermobility and the bone defects on the CT scan following shoulder dislocation. Bone defects were a risk factor for recurrence. There was no correlation between the Beighton Score and the tissue laxity. There was a correlation between the tissue laxity and the clinical assessment of laxity at the little finger MCPJ by using a force- goniometer system. There was a correlation between the collagen V expression in the dermal papillae of the skin and the Beighton score.