Hooke, Alexander W.

ABSTRACT Calcific tendinopathy is a common musculoskeletal disorder marked by calcium deposition within tendons, often accompanied by pain, impaired mobility, and in severe cases, ossification. However, the mechanisms underlying tendon mineralization remain poorly understood. In contrast to pathological human calcification, turkeys naturally develop tendon mineralization during growth without signs of inflammation or ossification. This study had two phases: an observational phase to assess onset and progression of calcification, and an interventional phase to evaluate the role of mechanical loading. In the observational phase, flexor tendons were collected from turkeys aged 1–16 weeks in a serial sacrifice study and analyzed by Von Kossa staining and biomechanical testing. Calcification began at 7 weeks, localized within organized collagen matrices, progressed through Weeks 8–14, and peaked by 16 weeks. In the interventional phase, nine female turkeys were randomized at 4 weeks into a transection group ( n = 3), sham group ( n = 3), and control group ( n = 3). Transection at the muscle–tendon junction eliminated mechanical loading. At 16 weeks, tendons were analyzed by histology, quantitative RT‐PCR, ICP‐MS, and biomechanical testing. Transected tendons showed a near‐complete absence of mineralization, reduced expression of osteogenic markers (osteopontin, osteocalcin, Runx‐2), and significantly lower calcium, magnesium, and phosphorus levels. Biomechanical testing indicated reduced stress relaxation, stiffness, and Young's modulus in the transected group. Tendon calcification in turkeys functioned as a mechanically regulated, nonpathological process. The study established a relevant model for early tendon mineralization and offered a basis for developing load‐dependent therapies for human tendon disease.

AimsPrevious studies have highlighted differences in the risk of periprosthetic fractures (PPFs) in patients undergoing total hip arthroplasty with either a cemented taper slip (TS) stem or a composite beam (CB) stem. This biomechanical study explored the occurrence of PPF around these stems, and the protective effect of adding a 16-gauge prophylactic calcar or diaphyseal wire to the TS stems to increase the resistance to torque as a potential way to prevent these fractures.MethodsA total of 21 TS stems (eight alone, six with calcar wiring, and seven with diaphyseal wiring placed 2 cm distal to the lesser trochanter) and seven CB stems were cemented into standard sawbones. The peak torque at failure was measured using a servohydraulic test machine, and the fracture location was recorded. An a priori power analysis determined that seven specimens per group were needed to detect a 30 Nm difference with 90% power, assuming a 14.8 Nm SD in peak torque between groups. Comparisons were performed using paired t-tests.ResultsCB stems exhibited a significantly higher mean peak torque at failure (205.3 Nm (SD 26.9)) than TS stems (159.5 Nm (SD 17.4); p = 0.012), calcar-wired TS (148.2 Nm (SD 38.6); p = 0.031), and diaphyseal-wired TS (164.9 Nm (SD 21.5); p = 0.027). This study did not demonstrate that wired-TS stems had a higher peak torque at failure than non-wired TS stems. Additionally, calcar wiring was not found to be stronger than diaphyseal wiring (p = 0.400). Four CB fractures occurred distal to the stem, whereas all TS fractures occurred at the mid-stem, simulating a Vancouver type B fracture. Interestingly, adding the diaphyseal wire shifted the fracture location more distally in four of the seven stems (p = 0.070).ConclusionIn this model, CB stems had greater resistance to torque than TS stems, which may explain the lower risk of PPF. Adding calcar or diaphyseal wires to the TS stems resulted in no significant change in peak torque to fracture. CB cemented stems should be considered in patients at high risk of PPF.Cite this article: Bone Joint J 2025;107-B(5 Supple A):32–37.

Background: No biomechanical study has established the effect of different graft positions or bone block options on anterior glenohumeral joint stability. Purpose/Hypothesis: The purpose of this study was to compare graft choice (distal clavicular vs coracoid autograft for Latarjet) and position on stability of the bone block for anterior glenohumeral instability. It was hypothesized that both grafts would be comparable if flush with the glenoid but that the sling effect of the Latarjet procedure would lead to greater stability in case of graft medialization. Study Design: Controlled laboratory study. Methods: Eight cadaveric shoulders were included. Defects stabilized using a distal clavicular graft and a coracoid graft were consecutively positioned at 0, 4, and 8 mm medially. The starting position was determined by the humeral head’s being seated at its most medial position on the glenoid surface. Each experiment comprised maximal external rotation and glenohumeral abduction at 60° while applying a constant 50-N medial compressive force to the humerus under all conditions. The conjoint tendon was routed through a split in the subscapularis and loaded with a 5-N weight using a pulley system for all Latarjet trials to simulate the sling effect. Results: Regarding the clavicular graft, the stability ratio significantly decreased versus the intact condition at all medial offsets ( P = .007 for 0 mm, P < .001 for 4 mm, and P < .001 for 8 mm), and it was significantly lower in the 4-mm versus 0-mm position ( P = .008), significantly higher in the 4-mm versus 8-mm position ( P < .001), and significantly lower in the 8-mm versus 0-mm position ( P < .001). Regarding the coracoid graft, the stability ratio was comparable with intact for the 0-mm position ( P = .12), while it was significantly lower in the 4-mm and 8-mm positions ( P < .001 for both). The distal clavicular graft at 0-mm offset was comparable with the coracoid graft at 0-mm offset. Conclusion: In shoulders with anterior glenoid bone loss, the coracoid and distal clavicular autografts were biomechanically comparable when placed flush with the glenoid. The distal clavicle at 0-mm offset did not restore stability compared with the intact specimen, but the Latarjet at 0-mm offset was not significantly different from the intact condition. Clinical Relevance: The Latarjet procedure provides higher stability compared with distal clavicular autograft when medialized.

Previous studies have highlighted differences in the risk of periprosthetic fracture between tapered slip (TS) and composite beam (CB) stems. This biomechanical study explored periprosthetic fractures around these stems and the effect of adding a 16-gauge calcar or diaphyseal wire to TS stems on their resistance to torque.A power analysis determined a sample size of 7 specimens per group, assuming a standard deviation of 14.8 Nm in peak torque, to provide 90% power to detect a difference of at least 30 Nm between groups. Twenty-one TS stems (eight alone, six with calcar wiring, seven with diaphyseal wiring placed 2 cm distal to the lesser trochanter) and seven CB stems were cemented into standard Sawbones. A servo-hydraulic test machine applied a 1000 N load with a 1-degree rotation per second until failure. The peak torque at failure was measured, and the fracture location recorded. Comparisons were performed using two-sample t-tests.CB stems exhibited a significantly higher peak torque at failure (205.3 Nm) than TS stems (159.5 Nm, p=0.020). Calcar-wire-TS (148.2 Nm, p=0.036) and diaphyseal-wire-TS (164.9 Nm, p=0.036) were both weaker than CB stems. Wired-TS stems showed no significant difference from non-wired-TS stems. Additionally, the study could not conclude that calcar wiring is stronger than diaphyseal wiring. All TS fractures occurred at the mid-stem, simulating a B-type fracture, while the addition of the diaphyseal wire shifted the fracture location more distally in four of seven stems (p=0.0699).This biomechanical study supports the clinical evidence that CB stems have stronger resistance to torque than TS stems and may explain lower risk of periprosthetic fracture. The addition of calcar or diaphyseal wires to TS stems resulted in no significant changes in peak torque to fracture. In patients at high risk of periprosthetic fracture, CB cemented stems should be considered.

Purpose To determine the relationship between cam morphology of the hip and ipsilateral sacroiliac motion compared to the native hip in a cadaveric model. Methods A simulated cam state was created using a 3‐dimensional printed cam secured to the head‐neck junction of 5 cadaveric hips. Hips were studied using a computed tomography–based optic metrology system and a 6 degree‐of‐freedom robot to exert an internal rotation torque at 3 different torque levels (6 N‐m, 12 N‐m, 18 N‐m). Outcomes included translational and rotational movement about 3 axes and composite (total) translational motion at the ipsilateral sacroiliac (SI) joint. Statistical analysis included a linear mixed model regression with repeated measures. Results The presence of a simulated cam was associated with medial motion in the coronal plane ( P = .03) and posterior motion in the sagittal plane ( P < .01) but not composite motion ( P = .37). Motion in the axial plane was in an inferior direction ( P = .08). Cam morphology significantly changed rotation in the sagittal plane ( P < .01) but not in the coronal ( P = .63) or axial plane ( P = .18). Composite motion was related to the amount of torque applied to the hip ( P < .01). The amount of torque applied to the hip was related to rotation in the coronal plane ( P < .01), axial plane ( P < .01), and sagittal plane ( P < .01) with increased effects as torque increased. Torque was not associated with translation movement in any of the anatomic planes. Conclusions The presence of simulated cam morphology is associated with motion in a more medial, inferior, and posterior direction at the ipsilateral SI joint relative to a native state. Increasing torque affects the magnitude of translation, but not its direction, which in this study is primarily influenced by cam morphology. Clinical Relevance This biomechanical connection between cam‐type femoroacetabular impingement syndrome and the ipsilateral SI joint provides insight into SI joint dysfunction in patients with femoroacetabular impingement syndrome.

Abstract Introduction The costo-osteochondral autograft, vascularized medial femoral trochlear osteochondral autograft, and proximal hamate autograft have been used for the reconstruction of unsalvageable proximal pole scaphoid nonunions. Our hypothesis is that there is no difference in carpal kinematics after the proximal pole of the scaphoid is reconstructed with these three graft options. Methods Wireless sensors were mounted to the carpus that was loaded through cyclical motion. Each specimen was tested under a series of the three reconstructed conditions and their kinematics compared. Results No significant differences were found in scapholunate and lunocapitate joint motion during wrist flexion-extension and wrist radioulnar deviation between the three reconstructed conditions (p > 0.05). Discussion and Conclusion There are minimal differences in carpal kinematics when comparing reconstruction of the proximal pole of the scaphoid with the costoosteochondral, medial femoral trochlear, and proximal hamate grafts.

Background: To determine the amount of micromotion during forearm rotation after diaphyseal ulnar shaft fracture or osteotomy. Methods: This was a biomechanical study using 7 paired-matched cadavers. The upper extremity was mounted in a custom rig and the forearm brought through full pronation and supination. A Hall effect sensor was placed at the fracture ends to measure micromotion for all tested conditions. There were 4 conditions tested: (1) intact ulnar shaft with plate to act as a control; (2) transverse fracture/osteotomy without stabilization; (3) fracture/osteotomy with cortical apposition stabilized with plate fixation; and (4) 50% comminuted fracture stabilized with plate. Results: There was a significantly greater amount of fracture site motion in the fracture/osteotomy model without stabilization compared with all other tested conditions ( P < .001, .0001, .0003, respectively). The fracture/osteotomy site with cortical apposition and the comminuted fracture models showed no statistically significant differences in the amount of micromotion compared with each another ( P = .952) or compared with the intact ulnar shaft ( P = .997, .889, respectively). Conclusions: There was no significant difference in the amount of motion between an intact ulnar shaft, an ulnar shaft fracture with cortical apposition stabilized with a plate, and a plated comminuted fracture. These findings may help surgeons decide on their type of postoperative immobilization in the setting of isolated ulnar shaft fractures or ulnar shaft osteotomies stabilized with plate fixation.

Purpose To investigate the gliding resistance dynamics between the supraspinatus (SSP) tendon and the coracoacromial arch, both before and after subacromial decompression (anterolateral acromioplasty) and acromion resection (acromionectomy). Methods Using 4 fresh‐frozen cadaveric shoulders, acromion shapes were classified (2 type I and 2 type III according to Bigliani). Subacromial bursa and coracoacromial ligament maintenance replicated physiologic sliding conditions. Gliding resistance was measured during glenohumeral abduction (0° to 60°) in internal rotation (IR) and external rotation (ER). Peak gliding resistance between the SSP tendon and the coracoacromial arch was determined and compared between intact, anterolateral acromioplasty, and acromionectomy. Results Peak SSP gliding resistance during abduction in an intact shoulder was significantly higher in IR than in ER (4.1 vs 2.1 N, P < .001). The mean peak SSP gliding resistance during 0° to 60° glenohumeral abduction in IR in the intact condition was significantly higher compared with the subacromial decompression condition (4.1 vs 2.8 N, P = .021) and with the acromionectomy condition (4.1 vs 0.9 N, P < .001). During 0° to 60° glenohumeral abduction in ER, mean peak SSP gliding resistance in the intact condition was not significantly different compared with the subacromial decompression condition (2.1 vs 2.0 N, P = .999). The 2 specimens with a hooked (i.e. type III) acromion showed significantly higher mean peak SSP gliding resistance during glenohumeral abduction in IR and ER when compared with the 2 specimens with a flat (i.e. type I) acromion (IR: 5.8 vs 3.0 N, P = .006; ER: 2.8 vs 1.4 N, P = .001). Conclusions In this cadaveric study, peak gliding resistance between the SSP tendon and the coracoacromial arch during combined abduction and IR was significantly reduced after anterolateral acromioplasty and was significantly higher in specimens with a hooked acromion. Clinical Relevance The clinical benefit of subacromial decompression remains unclear. This study suggests that anterolateral acromioplasty might reduce supraspinatus gliding resistance in those with a hooked acromion and in the typical “impingement” position.

Background: The objective of this study was to determine whether reconstruction of the proximal pole of the scaphoid with a proximal hamate graft restores native carpal kinematics. Methods: A cadaveric study was designed assessing wrist kinematic after proximal hamate graft for proximal pole of the scaphoid nonunion. Wireless sensors were mounted to the carpus using a custom pin and suture anchor system to 8 cadavers. A wrist simulator was used to move the wrist through a cyclical motion about the flexion/extension and radial/ulnar deviation axes. Each specimen was tested under a series of 3 conditions: (1) a native state, “Intact”; (2) fractured scaphoid proximal pole, “Fracture”; and (3) post-reconstruction of the proximal pole of the scaphoid using a proximal hamate graft, “Graft.” Results: The fracture condition resulted in a statistically significant change in scapholunate kinematics across the entire arc of motion relative to the intact condition. Reconstruction with proximal hamate grafts restored scapholunate kinematics close to the intact state in both flexion/extension and radial/ulnar deviation axes. The lunocapitate flexion during wrist flexion was significantly different after the hamate graft reconstruction. Conclusions: Proximal hamate to scaphoid transfer resulted in restoration of near normal carpal kinematics to the intact state.

Background: Tendons are primarily acellular, limiting their intrinsic regenerative capabilities. This limited regenerative potential contributes to delayed healing, rupture, and adhesion formation after tendon injury. Purpose: To determine if a tendon’s intrinsic regenerative potential could be improved after the application of a purified exosome product (PEP) when loaded onto a collagen scaffold. Study Design: Controlled laboratory study. Methods: An in vivo rabbit Achilles tendon model was used and consisted of 3 groups: (1) Achilles tenotomy with suture repair, (2) Achilles tenotomy with suture repair and collagen scaffold, and (3) Achilles tenotomy with suture repair and collagen scaffold loaded with PEP at 1 × 10 12 exosomes/mL. Each group consisted of 15 rabbits for a total of 45 specimens. Mechanical and histologic analyses were performed at both 3 and 6 weeks. Results: The load to failure and ultimate tensile stress were found to be similar across all groups ( P ≥ .15). The tendon cross-sectional area was significantly smaller for tendons treated with PEP compared with the control groups at 6 weeks, which was primarily related to an absence of external adhesions ( P = .04). Histologic analysis confirmed these findings, demonstrating significantly lower adhesion grade both macroscopically ( P = .0006) and microscopically ( P = .0062) when tendons were treated with PEP. Immunohistochemical staining showed a greater intensity for type 1 collagen for PEP-treated tendons compared with collagen-only or control tendons. Conclusion: Mechanical and histologic results suggested that healing in the PEP-treated group favored intrinsic healing (absence of adhesions) while control animals and animals treated with collagen only healed primarily via extrinsic scar formation. Despite a smaller cross-sectional area, treated tendons had the same ultimate tensile stress. This pilot investigation shows promise for PEP as a means of effectively treating tendon injuries and enhancing intrinsic healing. Clinical Relevance: The production of a cell-free, off-the-shelf product that can promote tendon regeneration would provide a viable solution for physicians and patients to enhance tendon healing and decrease adhesions as well as shorten the time required to return to work or sports.