Ski boot canting adjustments affect kinematic, kinetic, and postural control measures associated with fall and injury risk.

OBJECTIVES: The aim of this study was to investigate if and to what extent small lateral wedges inserted under the ski boot, known as canting, could impact knee kinematics/kinetics, balance, and neuromuscular activity in recreational alpine skiers in the laboratory setting. DESIGN: Experimental, crossover study with repeated-measures analysis METHODS: Thirty-eight recreational skiers completed a single-leg postural balance test while wearing standardized ski boots in their unmodified state (control), and with medial and lateral canting wedges applied. Kinematics, kinetics, postural control measures, and neuromuscular activity of the lower extremity were assessed using optical motion capture, instrumented force plates, and electromyography. RESULTS: Canting modifications had significant impact on lower extremity kinematics and kinetics: canting wedges on the medial side of the foot significantly decreased knee valgus moments, hip internal rotation, and hip adduction. Medial canting also improved some postural control measures associated with balance quality, and reduced activation levels of the Vastus Lateralis, Biceps Femoris, and Tibialis Anterior. CONCLUSIONS: In the laboratory setting, canting appears to be an appropriate option for improving balance in alpine skiers. Medial canting can alter skier kinematics and kinetics in ways which are consistent with mechanisms of ACL injury. Canting may also result in reduced neuromuscular effort. These changes in movement have potential to prevent lower limb injuries in alpine skiers. The findings of this study motivate future research to predict individual responses to canting treatment in a study setting more closely resembling the sports environment.

Wearable sensor validation of sports-related movements for the lower extremity and trunk.

Inertial Measurement Units (IMUs), an alternative to 3D optical motion capture, are growing in popularity to assess sports-related movements. This study validated an IMU system against a "gold-standard" optical motion capture system during common sports movements. Forty-nine healthy adults performed six movements common to a variety of sports applications (cutting, running, jumping, single leg squats, and cross-over twist) while simultaneously outfitted with standard, retroreflective markers and a wireless IMU system. Bias, RMSE, precision, and maximum absolute error (MAE) were calculated to compare the two systems at the lower extremity joints and the trunk in all planes of movement and for all activities. The MAE difference between fast and slow activities for the sagittal, transverse, and frontal planes were 11.62°, 7.41°, and 5.82°, respectively. For bias, the IMU system tended to report larger angles than the optical motion capture system in the transverse and frontal planes and smaller angles in the sagittal plane. Average intraclass correlation coefficients for the sagittal, transverse, and frontal planes were 0.81±0.17, 0.38±0.19, and 0.22±0.37, respectively. When calculating a global bias across all three planes, the IMU system reported nearly identical angles (< 3.5° difference) to the optical motion capture system. The global precision across all planes was 2-6.5°, and the global RMSE was 7-10.5°. However, the global MAE was 11-23°. Overall, and with suggestions for methodological improvement to further reduce measurement errors, these results support current applications and also indicate the need for continued validation and improvement of IMU systems.

Use of Platelet-Rich Plasma Immediately After an Injury Did Not Improve Ligament Healing, and Increasing Platelet Concentrations Was Detrimental in an In Vivo Animal Model.

BACKGROUND: Limited information in basic science and clinical trials exists to determine if ligament healing may be accelerated with the use of biological adjuvants, such as platelet-rich plasma (PRP). However, there has been widespread acceptance of PRP for use in clinical practice, despite an inadequate understanding of its biological mechanism of action. PURPOSE: To determine whether a single dose of PRP could accelerate ligament healing and correspondingly improve histological characteristics and biomechanical properties when injected immediately postoperatively into the injured medial collateral ligament (MCL) of New Zealand White rabbits. STUDY DESIGN: Controlled laboratory study. METHODS: Eighty skeletally mature New Zealand White rabbits (160 knees) were used. The MCL was torn midbody to simulate a grade 3 tear. After an acute injury of the MCL, the administration of autologous PRP at 3 different platelet concentrations (0 million/uL, platelet-poor plasma [PPP]; 0.6 million/uL, 2 times the baseline [2× PRP]; and 1.2 million/uL, 4 times the baseline [4× PRP]) was performed and compared with a saline injection control in the contralateral knee. Histological analysis and a biomechanical endpoint characterization were utilized to assess ligamentous healing and compare it to a sham surgery group. RESULTS: The PPP ( P = .001) and 4× PRP ( P = .002) groups had a significantly lower collagen subscore than the sham surgery group. No other differences were observed among the treatment groups, including the vascularity subscore and overall ligament tissue maturity index score. Compared with saline-injected contralateral knees, the maximum load for PPP and 2× PRP was not significantly different ( P = .788 and .325, respectively). The maximum load and stiffness for knees treated with 4× PRP were significantly less than for the saline-treated contralateral knees ( P = .006 and .001, respectively). CONCLUSION: One single dose of PPP or 2× PRP at the time of injury did not improve ligament healing. In addition, 4× PRP negatively affected ligament strength and histological characteristics at 6 weeks after the injury. CLINICAL RELEVANCE: The current practice of treating knee ligament injuries with PRP may not improve healing at low doses of PRP. The decreased mechanical properties and histological appearance of the torn MCL suggest that high doses of PRP decrease the quality of repair tissue. Further in vivo studies are necessary to determine the dosing and timing of PRP administration after a ligament injury before the widespread use of PRP to treat ligament injuries is recommended.

Biomechanical Comparison of 3 Glenoid-Side Fixation Techniques for Superior Capsular Reconstruction.

BACKGROUND: Superior capsular reconstruction (SCR) was recently introduced as a treatment for irreparable superior rotator cuff tears in younger patients. Purpose/Hypothesis: The purpose was to assess the biomechanical strength of 3 methods for fixation of the graft to the glenoid for SCR. It was hypothesized that a 4-anchor technique would provide greater load to failure than 3-anchor techniques. STUDY DESIGN: Controlled laboratory study. METHODS: Thirty-six cadaveric specimens were randomized into 3 groups of previously established glenoid-side graft fixation techniques: (1) three 3.5-mm knotless screw-in anchors, (2) three 3.0-mm knotless push-in anchors, and (3) a 4-anchor hybrid construct with two 3.0-mm knotted push-in anchors and two 2.9-mm knotless push-in anchors. The repairs were cyclically loaded at 0.5 Hz from 10 to 200 N, then pulled to failure. Elongation, stiffness, maximum load at failure, and mode of failure were recorded and calculated. RESULTS: There were no significant differences in graft elongation or stiffness among the 3 techniques ( P > .37 and P > .26, respectively). Maximum load to failure was significantly greater in technique 1 (mean ± SD, 427.85 ± 119.70 N) than technique 3 (319.5 ± 57.60 N) ( P = 0.024). There were no significant differences in load to failure between techniques 1 and 2 or between techniques 2 and 3. CONCLUSION: Glenoid-side graft fixation with 3 threaded 3.5-mm suture anchors showed a significant superior pull-out strength when compared with a 4-anchor hybrid technique and thus might be recommended in SCR for patients with irreparable superior rotator cuff tears to achieve maximum stability. CLINICAL RELEVANCE: SCR presents a novel alternative for treatment of irreparable superior rotator cuff tears in younger patients. Glenoid fixation is essential to provide adequate fixation of the graft to prevent the humeral head from rising and to restore normal biomechanics.

Intraarticular arthrofibrosis of the knee alters patellofemoral contact biomechanics.

BACKGROUND: Arthrofibrosis in the suprapatellar pouch and anterior interval can develop after knee injury or surgery, resulting in anterior knee pain. These adhesions have not been biomechanically characterized. METHODS: The biomechanical effects of adhesions in the suprapatellar pouch and anterior interval during simulated quadriceps muscle contraction from 0 to 90° of knee flexion were assessed. Adhesions of the suprapatellar pouch and anterior interval were hypothesized to alter the patellofemoral contact biomechanics and increase the patellofemoral contact force compared to no adhesions. RESULTS: Across all flexion angles, suprapatellar adhesions increased the patellofemoral contact force compared to no adhesions by a mean of 80 N. Similarly, anterior interval adhesions increased the contact force by a mean of 36 N. Combined suprapatellar and anterior interval adhesions increased the mean patellofemoral contact force by 120 N. Suprapatellar adhesions resulted in a proximally translated patella from 0 to 60°, and anterior interval adhesions resulted in a distally translated patella at all flexion angles other than 15° (p < 0.05). CONCLUSIONS: The most important finding in this study was that patellofemoral contact forces were significantly increased by simulated adhesions in the suprapatellar pouch and anterior interval. Anterior knee pain and osteoarthritis may result from an increase in patellofemoral contact force due to patellar and quadriceps tendon adhesions. For these patients, arthroscopic lysis of adhesions may be beneficial.

Functional Brace in ACL Surgery: Force Quantification in an In Vivo Study.

BACKGROUND: A need exists for a functional anterior cruciate ligament (ACL) brace that dynamically supports the knee joint to match the angle-dependent forces of a native ACL, especially in the early postoperative period. PURPOSE/HYPOTHESIS: The purpose of this study was to quantify the posteriorly directed external forces applied to the anterior proximal tibia by both a static and a dynamic force ACL brace. The proximal strap forces applied by the static force brace were hypothesized to remain relatively constant regardless of knee flexion angle compared with those of the dynamic force brace. STUDY DESIGN: Controlled laboratory study. METHODS: Seven healthy adult males (mean age, 27.4 ± 3.4 years; mean height, 1.8 ± 0.1 m; mean body mass, 84.1 ± 11.3 kg) were fitted with both a static and a dynamic force ACL brace. Participants completed 3 functional activities: unloaded extension, sit-to-stand, and stair ascent. Kinematic data were collected using traditional motion-capture techniques while posteriorly directed forces applied to the anterior aspect of both the proximal and distal tibia were simultaneously collected using a customized pressure-mapping technique. RESULTS: The mean posteriorly directed forces applied to the proximal tibia at 30° of flexion by the dynamic force brace during unloaded extension (80.2 N), sit-to-stand (57.5 N), and stair ascent (56.3 N) activities were significantly larger, regardless of force setting, than those applied by the static force brace (10.1 N, 9.5 N, and 11.9 N, respectively; P < .001). CONCLUSION: The dynamic force ACL brace, compared with the static force brace, applied significantly larger posteriorly directed forces to the anterior proximal tibia in extension, where the ACL is known to experience larger in vivo forces. Further studies are required to determine whether the physiological behavior of the brace will reduce anterior knee laxity and improve long-term patient outcomes. CLINICAL RELEVANCE: ACL braces that dynamically restrain the proximal tibia in a manner similar to physiological ACL function may improve pre- and postoperative treatment.

A Contact Pressure Analysis Comparing an All-Inside and Inside-Out Surgical Repair Technique for Bucket-Handle Medial Meniscus Tears.

PURPOSE: To directly compare effectiveness of the inside-out and all-inside medial meniscal repair techniques in restoring native contact area and contact pressure across the medial tibial plateau at multiple knee flexion angles. METHODS: Twelve male, nonpaired (n = 12), fresh-frozen human cadaveric knees underwent a series of 5 consecutive states: (1) intact medial meniscus, (2) MCL tear and repair, (3) simulated bucket-handle longitudinal tear of the medial meniscus, (4) inside-out meniscal repair, and (5) all-inside meniscal repair. Knees were loaded with a 1,000-N axial compressive force at 5 knee flexion angles (0°, 30°, 45°, 60°, 90°), and contact area, mean contact pressure, and peak contact pressure were calculated using thin film pressure sensors. RESULTS: No significant differences were observed between the inside-out and all-inside repair techniques at any flexion angle for contact area, mean contact pressure, and peak contact pressure (all P > .791). Compared with the torn meniscus state, inside-out and all-inside repair techniques resulted in increased contact area at all flexion angles (all P < .005 and all P < .037, respectively), decreased mean contact pressure at all flexion angles (all P < .007 and all P < .001, respectively) except for 0° (P = .097 and P = .39, respectively), and decreased peak contact pressure at all flexion angles (all P < .001, all P < .001, respectively) except for 0° (P = .080 and P = .544, respectively). However, there were significant differences in contact area and peak contact pressure between the intact state and inside-out technique at angles ≥45° (all P < .014 and all P < .032, respectively). Additionally, there were significant differences between the intact state and all-inside technique in contact area at 60° and 90° and peak contact pressure at 90° (both P < .005 and P = .004, respectively). Median values of intact contact area, mean contact pressure, and peak contact pressure over the tested flexion angles ranged from 498 to 561 mm2, 786 to 997 N/mm2, and 1,990 to 2,215 N/mm2, respectively. CONCLUSIONS: Contact area, mean contact pressure, and peak contact pressure were not significantly different between the all-inside and inside-out repair techniques at any tested flexion angle. Both techniques adequately restored native meniscus biomechanics near an intact level. CLINICAL RELEVANCE: An all-inside repair technique provided similar, native-state-restoring contact mechanics compared with an inside-out repair technique for the treatment of displaced bucket-handle tears of the medial meniscus. Thus, both techniques may adequately decrease the likelihood of cartilage degeneration.

The Proximal Tibiofibular Joint: A Biomechanical Analysis of the Anterior and Posterior Ligamentous Complexes.

BACKGROUND: Dislocation of the proximal tibiofibular joint is a complex injury that is often overlooked or misdiagnosed. Surgical management is recommended for severe acute or for chronic symptomatic instability of the proximal tibiofibular joint. Although the anterior ligamentous complex has been reported to be stronger than the posterior complex, biomechanical data are lacking. PURPOSE: To determine the ultimate load of the anterior and posterior ligamentous complexes of the proximal tibiofibular joint to determine optimal graft selection. STUDY DESIGN: Controlled laboratory study. METHODS: Ten nonpaired, fresh-frozen knee specimens were dissected to expose the anterior and posterior proximal tibiofibular ligamentous complexes. The tibia was split in the coronal plane to separate the anterior and posterior ligamentous complexes, and the fibula was left intact. Specimens were secured in a dynamic testing machine and preconditioned for 10 cycles between 2 and 10 N at 0.1 Hz followed by loading to failure at a rate of 25 mm/min. RESULTS: The mean (±SD) ultimate load of the anterior complex (517 ± 144 N) was significantly greater than the mean ultimate load of the posterior complex (322 ± 160 N) ( P = .012). The mean surface areas of the anterior and posterior complexes were 761 ± 174 mm2 and 565 ± 103 mm2, respectively ( P = .008). The mean values for stiffness of the anterior (133 N/mm) and posterior (109 N/mm) complexes were similar ( P = .250). CONCLUSION: The ligaments of the human proximal tibiofibular joint were able to withstand a mean ultimate failure load of 517 ± 144 N for the anterior complex and 322 ± 160 N for the posterior complex. In this regard, it is recommended that the strengths of grafts chosen for proximal tibiofibular reconstructions meet or exceed these values. CLINICAL RELEVANCE: The optimal surgical treatment for addressing residual proximal tibiofibular instability is not well defined. Before an anatomic reconstruction of the proximal tibiofibular ligament is developed, the individual biomechanical properties of the anterior and posterior ligamentous structures of the proximal tibiofibular joint need to be considered to facilitate an optimal reconstruction design.

Anatomic and Biomechanical Comparison of the Classic and Congruent-Arc Techniques of the Latarjet Procedure.

BACKGROUND: The Latarjet procedure is commonly performed using either the classic or the congruent-arc technique. Each technique has potential clinical advantages and disadvantages. However, data on the anatomic and biomechanical effects, benefits, and limitations of each technique are limited. Hypothesis/Purpose: To compare the anatomy and biomechanical fixation strength (failure load) between the 2 techniques. It was hypothesized that the classic technique would have superior initial fixation when compared with the congruent-arc technique and that this would be affected by sex and coracoid size. STUDY DESIGN: Controlled laboratory study. METHODS: A biomechanical cadaver study was performed with 20 pairs of male and female shoulders. One of each pair of shoulders was randomly assigned to receive the classic or congruent-arc technique. Coracoid and glenoid anatomic measurements were collected before biomechanical testing. A tensile force was applied through the conjoined tendon to replicate forces experienced by the coracoid graft in the early postoperative period, and the failure load was determined for each specimen. RESULTS: The mean ± SD surface area available for fixation was 263 ± 63 mm2 in the classic technique compared with 177 ± 63 mm2 in the congruent-arc group ( P < .001). 36% of the glenoid width was recreated in the classic group and 50% in the congruent-arc group ( P < .001). The congruent-arc technique resulted in a significantly lower ( P = .005) mean failure load (239 ± 91 N) compared with the classic technique (303 ± 114 N). Failure load was significantly higher in males ( P = .037); male specimens had a mean failure load of 344 ± 122 N for the classic technique and 289 ± 73 N for the congruent-arc technique, and females had a mean failure load of 266 ± 98 N and 194 ± 84 N, respectively. CONCLUSION: In this biomechanical model, the classic technique of the Latarjet procedure provided a greater surface area for healing to the glenoid and superior initial fixation when compared with the congruent-arc technique. The congruent-arc technique allowed restoration of a larger glenoid defect. CLINICAL RELEVANCE: The classic and congruent-arc techniques of coracoid transfer have anatomic and biomechanical advantages and disadvantages that should be considered when choosing between the 2 techniques.

Effect of Suture Caliber and Number of Core Strands on Repair of Acute Achilles Ruptures: A Biomechanical Study.

BACKGROUND: Controversy exists regarding the ideal Achilles rupture treatment; however, operative treatment is considered for athletes and active patients. The ideal repair construct is evolving, and the effect of suture caliber or number of core strands has not been studied. METHODS: Simulated mid-substance Achilles ruptures were performed in 24 cadavers. Specimens were randomized to three 6-core-strand style repair constructs: (1) 4 No. 2 sutures and two 2-mm tapes (2T); (2) 2 No. 2 sutures and four 2-mm tapes (4T); (3) 12 (double-6-strand) strand repair (12 No. 2-0 sutures [12S]). Repairs were subjected to a cyclic loading protocol representative of postoperative rehabilitation. These data were compared to a previously published standard open repair technique (6-core strands with No. 2 sutures) on 9 specimens tested under the same conditions.6 Results: No significant elongation differences were observed between the repair groups and the previously published standard repair group in the first 2 stages of the simulated rehabilitation protocol. Both the 2T and 12S repairs survived a significantly greater number of cycles to failure ( P = 0.0005, P = 0.0267, respectively) and had a significantly higher failure load ( P = .0005, P = .0118, respectively) compared to the previously published data. These 2 constructs consistently survived the advanced stages of the simulated rehabilitation protocol. The majority of repairs failed at the knots. CONCLUSIONS: In this study, the 2T and 12S constructs survived the later stages of our simulated rehabilitation protocol, suggesting that they may be able to accommodate a more aggressive clinical rehabilitation protocol. Substituting suture-tape for 2 core strands or doubling the core strands with a smaller-caliber suture created a biomechanically stronger construct. CLINICAL RELEVANCE: Achilles repair with an added nonabsorbable, high-tensile strength tape allowed for a stronger construct that may allow for a more aggressive, early rehabilitation protocol and earlier return to function.

Hip Capsular Closure: A Biomechanical Analysis of Failure Torque.

BACKGROUND: Hip capsulotomy is routinely performed during arthroscopic surgery to achieve adequate exposure of the joint. Iatrogenic instability can result after hip arthroscopic surgery because of capsular insufficiency, which can be avoided with effective closure of the hip capsule. There is currently no consensus in the literature regarding the optimal quantity of sutures upon capsular closure to achieve maximal stability postoperatively. Purpose/Hypothesis: The purpose of this study was to determine the failure torques of 1-, 2-, and 3-suture constructs for hip capsular closure to resist external rotation and extension after standard anterosuperior interportal capsulotomy (12 to 3 o'clock). Additionally, the degree of external rotation at which the suture constructs failed was recorded. The null hypothesis of this study was that no significant differences with respect to the failure torque would be found between the 3 repair constructs. STUDY DESIGN: Controlled laboratory study. METHODS: Nine pairs (n = 18) of fresh-frozen human cadaveric hemipelvises underwent anterosuperior interportal capsulotomy, which were repaired with 1, 2, or 3 side-to-side sutures. Each hip was secured in a dynamic biaxial testing machine and underwent a cyclic external rotation preconditioning protocol, followed by external rotation to failure. RESULTS: The failure torque of the 1-suture hip capsular closure construct was significantly less than that of the 3-suture construct. The median failure torque for the 1-suture construct was 67.4 N·m (range, 47.4-73.6 N·m). The median failure torque was 85.7 N·m (range, 56.9-99.1 N·m) for the 2-suture construct and 91.7 N·m (range, 74.7-99.0 N·m) for the 3-suture construct. All 3 repair constructs exhibited a median 36° (range, 22°-64°) of external rotation at the failure torque. CONCLUSION: The most important finding of this study was that the 2- and 3-suture constructs resulted in comparable biomechanical failure torques when external rotation forces were applied to conventional hip capsulotomy in a cadaveric model. The 3-suture construct was significantly stronger than the 1-suture construct; however, there was not a significant difference between the 2- and 3-suture constructs. Additionally, all constructs failed at approximately 36° of external rotation. CLINICAL RELEVANCE: Re-establishing the native anatomy of the hip capsule after hip arthroscopic surgery has been reported to result in improved outcomes and reduce the risk of iatrogenic instability. Therefore, adequate capsular closure is important to restore proper hip biomechanics, and postoperative precautions limiting external rotation should be utilized to protect the repair.

High-load preconditioning of human soft tissue hamstring grafts: An in vitro biomechanical analysis.

PURPOSE: In order to minimize viscoelastic elongation of ACL reconstruction grafts, preconditioning protocols have been employed in clinical practice prior to final graft fixation. The purpose of this study was to evaluate two separate high-load static preconditioning protocols of double-looped semitendinosus-gracilis grafts and compare these results to both a current clinical protocol and a control group with no preconditioning protocol applied. It was hypothesized that a high-load, static preconditioning protocol would minimize graft elongation during a simulated progressive early rehabilitation compared to both the "89 N" clinical protocol and control groups. METHODS: Grafts were randomly allocated into four preconditioning study groups: (1) control (no preconditioning), (2) clinical protocol (89 N for 15 min), (3) high-load, short duration (600 N for 20 s), and (4) high-load, long duration (600 N for 15 min). After preconditioning, grafts were cyclically loaded between 10 and 400 N at 0.5 Hz for 450 cycles to simulate early postoperative rehabilitation. Graft displacement (elongation) was recorded during both preconditioning and cyclic loading. RESULTS: Increased preconditioning load magnitude and duration significantly reduced graft elongation during cyclic loading (p < 0.05) which corresponded to an inverse relationship with increased elongation during preconditioning. The "600 N for 15 min" protocol resulted in significantly less elongation during simulated early rehabilitation than both the control group and the "89 N for 15 min" protocol (p < 0.001, p < 0.05). CONCLUSIONS: Graft elongation during simulated early rehabilitation was significantly reduced by a high-load preconditioning protocol applied for an extended period of time compared to a current common clinical protocol and grafts that were not preconditioned. In addition, the amount of elongation during simulated early rehabilitation was similar between grafts preconditioned using the current clinical practice protocol and the high-load/short-duration protocol, implying that the latter could potentially induce the same viscoelastic changes in soft tissue grafts as the current clinical practice. The "600 N for 20 s" preconditioning protocol may provide similar postoperative results as the clinical protocol, "89 N for 15 min", and also reduce or maintain operative time. A high-load preconditioning protocol that reduces graft elongation may benefit patients undergoing ACL reconstruction, especially for cases of failed primary reconstruction, genu recurvatum, and increased tibial slope, where maintaining graft length is imperative to restore knee stability.

Impact of Arthroscopic Lateral Acromioplasty on the Mechanical and Structural Integrity of the Lateral Deltoid Origin: A Cadaveric Study.

PURPOSE: To determine whether a 5-mm and/or 10-mm arthroscopic lateral acromioplasty (ALA) would weaken the structural and mechanical integrity of the lateral deltoid. METHODS: The acromion and lateral deltoid origin were harvested from 15 pairs (n = 30) of fresh-frozen human cadaveric shoulder specimens. One side of each specimen pair (left or right) was randomly assigned to either a 5-mm (n = 7) or 10-mm (n = 8) ALA group, and the contralateral sides (n = 15) were used as matched controls. Acromion thickness and width were measured pre- and postoperatively. After ALA, specimens were inspected for damage to the lateral deltoid origin. Each specimen was secured within a dynamic testing machine, and the deltoid muscle was pulled to failure. Statistical analysis was performed to determine whether ALA reduced the lateral deltoid's failure load. RESULTS: There was no significant difference in failure load between the 5-mm ALA group (661 ± 207 N) and its matched control group (744 ± 212 N; mean difference = 83 N; 95% confidence interval [CI], -91 to 258; P = .285) nor between the 10-mm ALA group (544 ± 210 N) and its matched control group (598 ± 157 N; mean difference = 54 N; 95% CI, -141 to 250; P = .532). There was no correlation found between the amount of bone resected (measured by percent thickness and width of the acromion after ALA) and the failure load of the deltoid. Visual evaluation of the acromion after ALA revealed the lateral deltoid origin had no damage in any case. CONCLUSIONS: ALA did not weaken the structural or mechanical integrity of the lateral deltoid origin. Neither a 5-mm nor a 10-mm ALA significantly reduced the deltoid's failure load. The lateral deltoid origin was not macroscopically damaged in any case. CLINICAL RELEVANCE: ALA can be performed without the potential risk of macroscopically damaging the lateral deltoid origin or reducing its failure load.

Biomechanical Comparison of Surgical Techniques for Resection Arthroplasty of the Sternoclavicular Joint.

BACKGROUND: The optimal location and extent of medial clavicle resection for sternoclavicular (SC) joint resection arthroplasty are unknown. HYPOTHESIS: Resection of the intra-articular disc alone cannot reliably decompress the SC joint, and a parallel resection technique will decompress the SC joint significantly more compared with the same amount with an oblique resection technique. STUDY DESIGN: Controlled laboratory study. METHODS: Force transmission through the SC joint was measured in 7 matched-pair human cadaveric SC joints in a dynamic tensile testing machine. The specimens were randomized to either a parallel or an oblique resection technique. An 80-N axial load was applied on the lateral clavicle toward the SC joint in each of the following 4 conditions: (1) intact joint, (2) after resecting the intra-articular disc, (3) after resecting 5 mm of the medial clavicle, and (4) after 10-mm resection. RESULTS: Complete discectomy of all SC joints resulted in a significant reduction of force transmitted through the SC joint (P = .002). However, the varying anatomy of the disc was accompanied by a varying amount of joint decompression (95% CI, 29.8%-65.4%). Resecting 5 mm of the SC joint with the parallel technique decompressed the SC joint by a mean (±SD) of 76.7 ± 22.1 N compared with 37.8 ± 24.8 N with the oblique technique (P = .02). Decompression did not significantly differ between the groups after 10-mm resection (P = .18) using the parallel technique (89.4 ± 24.1 N) compared with the oblique technique (68.2 ± 31.6 N). Furthermore, 5-mm resection of the medial end of the clavicle with the parallel technique decompressed the SC joint by an amount similar to 10-mm resection with the oblique technique. CONCLUSION: Resection of the disc alone did not reliably decompress each SC joint. Resection of 5 mm of the medial end of the clavicle with the parallel resection technique reliably decompressed the SC joint better than with the oblique resection technique. CLINICAL RELEVANCE: This study provides baseline data on SC joint resection techniques and their mechanical effects. This knowledge can be implemented in clinical practice to treat patients with symptomatic posttraumatic arthritis of the SC joint.