Following anterior cruciate ligament reconstruction (ACLR) using a semitendinosus (ST) autograft measures such as length, cross-sectional area, and volume may not fully describe the effects of tendon harvest on muscle morphology as these discrete measures cannot characterize three-dimensional muscle shape. This study aimed to determine between-limb ST shape similarity and regional morphology in individuals with a unilateral history of ACLR using a ST graft, and healthy controls.

A secondary analysis of magnetic resonance imaging was undertaken from 18 individuals with unilateral history of ST ACLR and 18 healthy controls. ST muscles were manually segmented, and shape similarity were assessed between limbs and groups using Jaccard index (0-1) and Hausdorff distance (mm). ST length (cm), peak cross-sectional area (CSA) (cm²), and volume (cm³) was compared between surgically reconstructed and uninjured contralateral limbs, and between the left and right limbs of control participants with no history of injury. Cohen's d was reported as a measure of effect size.

Compared to healthy controls, the ACLR group had significantly (p<0.001, d= −2.33) lower bilateral ST shape similarity. Furthermore, the deviation in muscle shape was significantly (p<0.001, d= 2.12) greater in the ACLR group. Within the ACLR group, maximum Hausdorff distance indicated ST from the ACLR limb deviated (23.1±8.68 mm) from the shape of the healthy contralateral ST, this was observed particularly within the distal region of the muscle. Compared to the uninjured contralateral limb and healthy controls, deficits in peak cross-sectional area and volume in ACLR group were largest in proximal (p<0.001, d= −2.52 to −1.28) and middle (p<0.001, d= −1.81 to −1.04) regions.

Findings highlight morphological features in distal ST not identified by traditional discrete morphology measures. ST shape was most different in the distal region of the muscle, despite deficits in CSA and volume being most pronounced in proximal and middle regions. ST shape following ACLR may affect force transmission and distribution within the hamstrings and contribute to persistent deficits in knee flexor and internal rotator strength.

Anterior cruciate ligament reconstruction (ACLR) using a semitendinosus (ST) autograft, with or without gracilis (GR), results in donor muscle atrophy and varied tendon regeneration. The effects of harvesting these muscles on muscle moment arm and torque generating capacity have not been well described. This study aimed to determine between-limb differences (ACLR vs uninjured contralateral) in muscle moment arm and torque generating capacity across a full range of hip and knee motions.

A secondary analysis of magnetic resonance imaging was undertaken from 8 individuals with unilateral history of ST-GR ACLR with complete ST tendon regeneration. All hamstring muscles and ST tendons were manually segmented. Muscle length (cm), peak cross-sectional area (CSA) (cm²), and volume (cm³) were measured in ACLR and uninjured contralateral limbs. OpenSim was used to simulate and evaluate the mechanical consequences of changes in normalised moment arm (m) and torque generating capacity (N.m) between ACLR and uninjured contralateral limbs.

Compared to uninjured contralateral limbs, regenerated ST tendon re-insertion varied proximal (+) (mean = 0.66cm, maximum = 3.44cm, minimum = −2.17cm, range = 5.61cm) and posterior (+) (mean = 0.38cm maximum = 0.71cm, minimum = 0.02cm, range = 0.69cm) locations relative to native anatomical positions. Compared to uninjured contralateral limbs, change in ST tendon insertion point in ACLR limbs resulted in 2.5% loss in peak moment arm and a 3.4% loss in peak torque generating capacity. Accounting for changes to both max isometric force and ST moment arm, the ST had a 14.8% loss in peak torque generating capacity.

There are significant deficits in ST muscle morphology and insertion points following ST-GR ACLR. The ST atrophy and insertion point migration following ACLR may affect force transmission and distribution within the hamstrings and contribute to persistent deficits in knee flexor and internal rotator strength.

Total knee replacement (TKA) surgery is an excellent and well-proven procedure for the treatment of end stage arthritis of the knee. Many refinements have taken place over time in an attempt to improve the components, wear qualities of the polyethylene, and the surgical technique to improve accuracy of component positioning, reduce patient pain, improve postoperative range of motion, ultimately improve results and to prolong the time until revision surgery may occur. This study examines the results of a gap balancing surgical technique in which components were implanted that had a posterior cruciate substituting design. This technique is performed with exacting alignment and balancing of the flexion and extension gaps prior to implantation of the knee components. The follow up is at a minimum of ten years.

515 consecutive knee replacements were followed prospectively for a minimum of ten years. The average age at surgery was 70 years, 73% of patients were female, with an average BMI of 31. All patients carried a diagnosis of osteoarthritis and a cemented, posterior stabilized design TKA (Balanced Knee System, Ortho Development) was implanted. All cases were performed by one of two experienced joint replacement surgeons.

The surgical technique demanded flexion and extension gap balancing as well as soft tissue balancing prior to finishing cuts being performed on the femoral side (See figures 1 and 2). Polyethylene spacers come in 1 millimeter increments.

28% of patients died postoperatively at an average of 7.4 years. These patients were older on average at the time of index surgery (76.6 years). None had undergone revision surgery. Of the remaining patients Knee Society scores (39 preop to 91 post op at ten years), function scores and range of motion all improved significantly. What's more, these results were not diminished at ten years. There were no component failures and less than 1% radiographic progressive lucent lines. Eleven revision surgeries (2.1 %) were performed with 2 acute superficial wound revisions, 3 late infections, one patellar tendon disruption from a fall at 7 years (BMI 45.7), 2 complete revisions performed elsewhere for unsatisfactory results, and 3 spacer exchanges for perception of postoperative laxity.

For the current study we also examined subgroups of the morbidly obese, octogenarians, and those with a preoperative valgus deformity of greater than 15%. At follow-up these subgroups fared very well with the exception of the heaviest BMI's being limited in range of motion because of soft tissue impingement.

Results suggest that this balancing technique gives excellent results with few complications at ten year evaluation. We believe that careful attention to bony and soft tissue balancing and equalization of gaps in flexion and in extension will prove beneficial for TKA longevity in even longer-term evaluation.

Figures 1 and 2 demonstrate gap balancing blocks and alignment rods in extension and in flexion